Mark Suster is running late. Sitting in his Mercedes-Benz CLS63 AMG, he surveys the traffic on West Sunset Boulevard through mirrored sunglasses. When his cell phone rings, Suster apologizes to the caller, an up-and-comer in Silicon Valley. "I'm sorry," he says. "I had a crazy morning."

This was no exaggeration. That morning in May, Suster had attended a business summit with South Korean President Park Geun-hye, raced to a taping of a Wall Street Journal webcast co-starring social-media mogul Gary Vaynerchuk, and attended two meetings with start-up founders. Now, he is speeding off to give a talk at the Hollywood Roosevelt Hotel.

When the conversation with the caller turns to term sheets, Suster's tone goes from apologetic to irritated. "You earn the right, through success, to get the kind of terms and protections you want. But you don't even have a product," he lectures. "You're not at the point in your career where you get to act like a prima donna." With that, Suster ends the call, leaves his car with the valet, and strides into the hotel to make his presentation.

Suster (rhymes with rooster) is in high demand these days. The entrepreneur-turned-investor is best known for Both Sides of the Table--the brash, opinionated, and gleefully obscene blog he has been writing since 2009.

Being a founder, Suster says, means enduring long days of anxiety, exhaustion, airport delays, and bad fast food. It means staving off creditors and working with less than nine months' worth of cash in your family's or company's bank account at any given time.

Co-managing partner at Los Angeles venture capital firm GRP Partners, he has built his name into a powerful brand, much of which is based on his hype-deflating candor. Suster, 45, has a talent for tipping sacred cows--and, on occasion, infuriating his readers.

On his blog, founders who waste time strutting around industry gatherings are "conference hos." Businessmen who smile, shake hands, and then eviscerate you are "grin f--ers." For an entrepreneur, becoming a VC means "going to the dark side." Suster keeps a reminder of this last phrase--a Darth Vader bobblehead doll--on the windowsill of his corner office. "If you never piss anybody off, you're not trying hard enough," he says. "And I piss people off on a regular basis."

Suster wrote one of his most popular blog posts, "Entrepreneurshit," on a sleepless night in November after returning from a weeklong business trip. The post dismantled the kind of glamorous fantasies about start-up life that are perpetuated by the tech press and celebrity entrepreneurs.

"If you read the tech press every day, you'd get the impression that it's all glamor. It's not," he wrote. Being a founder, he continued, means enduring long days of anxiety, exhaustion, airport delays, and bad fast food. It means staving off creditors and working with less than nine months' worth of cash in your family's or company's bank account at any given time.

It means tamping down your insecurities long enough to persuade potential employees, customers, and investors to take a huge gamble on you. All of this in pursuit of a vision that, statistically, stands only the slimmest chance of success. "No, it's not as bad as working in coal mines," he wrote in the post. "But it is quite the roller coaster, and the stress is real."

In fact, most entrepreneurs shouldn't seek the "rocket fuel" of venture capital, he says, firmly and often. Many businesses haven't yet maximized what they can do without it, and some businesses just aren't made to scale.

And there's nothing wrong, he says, with starting a company that's not positioned for massive growth, even if folks in Silicon Valley may deride it as a "lifestyle business." His take on venture capitalists? "The VC industry is very lemmingish," he says. "They find a trend and then everyone does it. But the Internet is a winner-take-most market. So you either back the winner, or you don't have outsize returns."

Six years ago, Suster was a new and relatively unknown player in venture capital. He had built and sold two businesses--the second, a content-management company called Koral, was acquired by joining his mentor and longtime investor, Yves Sisteron, as a partner at GRP.

His original plan was to move with his wife and two young sons to Los Angeles, spend a couple of years there learning the game from his fellow partners, then head home to open a satellite office in Silicon Valley.

But around 18 months into the work, he had a revelation. "I realized, Why on earth would I go to Silicon Valley and compete with 80 other firms on Sand Hill Road, when here we're the largest VC in town?" Suster recalls. "We have amazing entrepreneurs at our doorstep and very limited venture capital. There was this enormous opportunity."

Besides, when he looked back over the trajectory of Internet-era innovation, he saw how the focus had shifted from Web infrastructure (routers, switches, and the like) to what he calls the three C's--content, communication, and commerce, sectors that haven't historically been dominated by Silicon Valley. Los Angeles, he says, "is the content capital of the world in terms of film and television."

So he stayed put, dedicating himself to helping build the city's nascent tech scene. In 2009, he founded Launchpad LA, a mentorship network that encourages start-ups to grow locally--and stay local.

This evolved into an accelerator, which now offers young businesses up to $100,000 apiece and free space in an airy, open-plan office in Santa Monica, one block from the beach. (Notable alumni include Chromatik, maker of an iPad app and Web-based learning platform for musicians that is used on American Idol, and Sometrics, a company that helps publishers monetize online games using virtual currency and was acquired in 2011 by American Express.)

Launchpad invested in 18 start-ups last year; the companies ended up raising more than $30 million combined in outside capital.

Of course, exposure, Suster-style, isn't always flattering. Sam Teller, Launchpad LA's managing director, still remembers what happened two years ago, when Suster introduced him to Courtney Holt, the former president of Myspace Music.

Holt had just signed on as the chief operating officer at Maker Studios, a GRP portfolio company whose YouTube videos, including the blockbuster "Epic Rap Battles of History," together get more than three billion views a month. After the introduction, Teller emailed Holt to ask him out for lunch. The next morning, he recalls, Suster published a blog post titled "Never Ask a Busy Person to Lunch."

The post didn't out Teller by name, but the message was clear: Lunch lasts too long. It imposes on a busy person's schedule. Try coffee instead. (Teller wasn't offended, but a flame war broke out in response to the post. Commenters called Suster's stance "Machiavellian bullshit" and told him to "get over himself.")

Today, Suster is one of the most influential tech investors on the Web. He is often mentioned alongside--and linked by--the two VC-blogger titans he came up admiring: Brad Feld of the Foundry Group in Boulder, Colorado; and Fred Wilson of New York City's Union Square Ventures.

Feld first blogged about Suster in 2006, when Suster was still running his second company; Suster had lambasted a group of venture capitalists who started a meeting 30 minutes late and then barely paid attention to him.

For that, Gawker founder Nick Denton gave Suster a "hero award" on the Valleywag website. "I'm just glad I don't appear to be one of the assholes he met with," Feld wrote.

Suster's credibility comes from hard-won wisdom. In the aftermath of the dot-com collapse in 2000, he was forced to lay off more than half of the 92-person staff of his first company, BuildOnline, which made collaboration tools for the construction industry in Europe. "I cut some of my closest friends," he says. He was devastated.

Not long before, he had attended the Fortune Global Forum at the Palace of Versailles in France, where he dined alongside Michael Dell and sipped champagne in the private wine cellars of Bernard Arnault, the chief executive of French luxury group LVMH. "I drank my own Kool-Aid," he says. "I thought we were changing the world."

Six months later, no one would return his calls. The economy had taken a dive, and companies were less open to spending money on newfangled Web software. On top of those challenges, BuildOnline had grown too quickly. It had raised too much money, hired too many employees, and charged customers too much.

So austerity set in. Suster went from staying in high-end hotels to a 20-euro-a-night dump in Frankfurt, where guests had to step out into the snow to reach the communal bathrooms. "It was freezing, f--ing cold, and there were these Turkish construction workers with leopard-print underwear--like bikini-style underwear--going to shower with me, and I was like, 'What am I doing?' "Suster recalls.

Sisteron, his mentor and investor at GRP, watched him struggle. "Nothing teaches you more than that kind of punishment," Sisteron says. "He survived. He matured."

Now, Suster brings his unvarnished perspective to young entrepreneurs. A few hours after meeting South Korea's president in May, he commandeers a conference room at the Santa Monica offices of Burstly, one of GRP's portfolio companies. Two entrepreneurs--Salmaun Ahmad, 32, and Jamal Ashraf, 29--walk in to discuss their start-up, Advocus.

They had just moved from San Francisco to spend four months at Launchpad LA, where Suster had met them the week before. Ahmad nervously recaps Advocus's mission: helping businesses put potential clients in touch with their best customers for recommendations. "Every company has advocates and evangelists," he tells Suster. "We're making those advocates accessible in the sales process."

Suster, who was double fisting Diet Dr Pepper and coffee, interjects between bites of his turkey sandwich. He likes the idea but is skeptical about the implementation. "My best customers ought not be talking to the unwashed masses," he says. "And my medium and worst people ought not be talking to anybody.

I don't have all the answers. I don't pretend that I do. I'm just here to spar with you and make sure you're thinking about it the right way." Ahmad responds, "We hear you loud and clear." They agree to meet again.

Next, Suster walks down the hall to Burstly's rec room. On a couch beside Ping-Pong and foosball tables, he meets with Arye Barnehama and Laura Michelle Berman. Their start-up, Melon, makes a brainwave-measuring headband that works with a mobile app to help users gauge their concentration. "It's about turning the invisible activity of your mind visible in a meaningful way," Barnehama explains. "Almost like a 21st-century journal."

Suster likes the idea, wondering aloud if Melon could help kids with attention disorders. (Suster himself has ADD.) But did it really have to be a headband? "It kind of needs something that makes it feel less like, 'I'm John McEnroe,' " he quips.

Suster loves this kind of work. "I get paid to have the smartest people I know come to my office and hear how they want to change the world," he said. "And if I don't like the idea, I don't have to spend any more time with them."

He misses being an entrepreneur, but he says he sleeps better as a VC. "The highs are more muted, the lows are a little less panic driven," he explains. Having a bunch of start-ups in his portfolio dilutes his personal risk.

This spring, GRP promoted Suster to co-managing partner. With a young protégé, Jordan Hudson, he is preparing to rebrand the 17-year-old firm, which will be renamed Upfront Ventures, in a way that will emphasize openness, transparency, and strong opinions. In a sense, this project is his latest start-up. Its offices will move from buttoned-up Century City to lively Santa Monica, a hot spot in the Los Angeles start-up scene.

Not that Suster has to be there to connect. Thanks to his blog, he gets cold pitched by strangers everywhere these days. They collar him when he walks down the street at South by Southwest or when he is dining with his wife at a restaurant in New York City.

That busy day in May is no different. That night, he attends a party at YouTube Space, a 41,000-square-foot Playa Vista aircraft hangar, to honor Cenk Uygur, co-founder of the Young Turks online news network, which has just reached one billion views.

After the party, Suster is waiting for a valet to pull his car around when he is rushed by the founder of a digital media start-up from Irvine, California. "I recognize you by your image," the man gushes. After 14 hours straight of accessibility and blunt talk, Suster is eager to get home to his family in Pacific Palisades. But he stands still, nodding patiently as he listens to the pitch.

That's the contradiction in Suster. Beneath the tough talk, many of his critiques are meant as tough love. Case in point: A week after he chastised the "prima donna" from Silicon Valley on the phone, he had an update. With Suster as the sponsoring partner, GRP would lead a $2 million round of financing for the company, which is set to debut this year. "Remember that guy I was talking to in the car?" he says. "We did sign a term sheet in the end. I got him to be reasonable."

Susterspeak: Here are some Susterisms defined

Entrepreneurshit. The unglamorous reality of start-up life.

Ballers on a budget. Founders who lease fancy cars as they rack up credit card bills.

Elephant hunters. Start-ups that focus on landing massive customers with enough "meat" to feed them for a long time. Instead, Suster says, you should hunt for deer--clients that are easier to catch but still have plenty of meat.

Gym salesmen VCs. VCs who pressure you to sign a term sheet in a couple of days and allude to pulling the deal if you don't.

Seagulls. Investors who know enough about your project to have an opinion but not enough to help. They swoop in for one day to check in, shit on you, and fly away.