We’re watching these five CEOs because they’re almost guaranteed to make news in 2013. Some of them are already pretty famous. Others we know pretty well at Inc., but are likely to be discovered by the rest of the world this year.

Here’s our list.

Mark Zuckerberg, age 28

Here we go again. What’s the headline now?  I know: Mark, Mark Mark. But this is the year we see whether Facebook can live up to its potential. The site has more traffic than Google, Yahoo, YouTube, Microsoft, and Amazon combined. It also has more personal information about its visitors than any of those other sites. But Facebook’s challenge--still--is to convert all that traffic and all that data into profits. It’s still trading on potential, and in 2013, it’s time to see movement towards realizing that potential.

What does the boy wonder need to accomplish this year? Zuckerberg is only 28 and he’s the CEO of a $56 billion corporation. He needs to mature into the role--put on his big-boy CEO pants. So far he has done some things that would not be considered best practices: the purchase of Instagram, for example, without much consultation. He’s continually facing backlash over privacy issues and is cagey about Facebook’s priorities on the subject. This year we’ll get a glimpse into whether he’s the next Jeff Bezos or the next Jerry Yang.

What special obstacles does he face? This drama will play out in a tough atmosphere for any leader. Because of his company’s size and Zuckerberg’s wealth and youth, no one will cut him slack. How many CEOs have been dramatized by Aaron Sorkin and appeared on SNL while they’re still in their 20s? That limelight comes with a price. He’ll be criticized by someone, no matter what he does, for violating privacy or acting monopolistic. Some are saying that Facebook has lost its edge in innovation. That will make his job that much tougher.

 Marissa Mayer, 37

What’s the story with her? Remember the famous headline in the Onion after Obama was elected in 2008? “Black man given toughest job in America?” Well, Marissa Mayer’s headline could be “Young pregnant blonde given toughest job in business.” Yahoo is a mess, and in 2013 the world will be watching whether she can turn it around.

What’s the issue with Yahoo? Yahoo’s not quite a laughingstock yet. It’s still a major force, with 60 million unique users a month. But that’s not as much scale as Facebook or Google, and Yahoo doesn’t know as much about those users as their chief competition.

How’s she doing so far? By all accounts, well. She’s made good hires, including Henrique DeCastro, whom she worked with at Google--one of several moves meant to reinstate Yahoo’s reputation as a technology leader. The revamping of Flickr, Yahoo’s photo sharing site, has been well received. So, so far so good.

Any special challenges for her? We won’t mince words: She will be under scrutiny because she’s a woman. In her 30s. And now with a baby, she’ll be for better or worse held up as an example of family life and work balance. That’s a distraction that a man in that job wouldn’t face.

Jack Dorsey, 36

What’s the headline on Dorsey, best known as the Twitter guy? Dorsey is the entrepreneur’s entrepreneur. He co-founded a social media platform that has been used to literally change the world, overthrow governments, and transform how people communicate. You’ve got to admire him for the audacity of his new venture, Square, which aims to preside over the end of cash, and take on the credit card establishment in the process. The guy’s got guts.

What is Square, exactly? If you’re not familiar with it, Square is a suite of apps that allow merchants to process credit cards and track their cash flow at a kind of mobile register. For consumers, it’s a way to pay for things using an app on their mobile phones.

What are the issues there? It’s hard because you have to convince two people---the merchant and the consumer--to use your product. Plus, there's a lot of competition: Paypal has a competing product. So does Intuit, and AT&T, T-Mobile and Verizon have joined to produce their own mobile payments system, called Isis.

How’s he doing so far? He’s been able to raise a lot of money, including from Marissa Mayer, one of his angel investors, and the company is valued at $3 billion plus, so a lot of people believe in him. And Square already says it has processed $8 billion in payments. He scored a huge win by striking a deal with Starbucks as their mobile payments system. If Square becomes the mobile payments platform, that would be huge.

Phil Libin, 40s

So who’s this guy again? Phil Libin may be the most underrated CEO in Silicon Valley. His company is Evernote, a suite of apps that help you store anything you want to remember and then retrieve it quickly. People who use Evernote tend to swear by it. It could be on its way to becoming a household name.

How does Evernote make money? Using a freemium model. But, unlike some other freemium-based companies, Evernote has had enormous success getting people to upgrade. Something like 25% of original users upgraded within a couple of years, which is off the charts for this model. It’s a sign that people really fall in love with the product. 

How’s it doing so far? The company is valued at over $1 billion and has been raising money and making acquisitions. Libin has said that he plans to go public--in fact, he says it’s inevitable--but he is coy about the timing. It could be this year, which is what I would keep an eye out for.

Alberto Perlman, 35

I’ve never heard of him. Who's Perlman? Alberto Perlman is the CEO of Zumba Fitness, which he founded with three partners, all of them named Alberto. But Perlman is the business brains of the outfit.

Okay, I know Zumba. What’s the headline? Zumba was Inc’s company of the year for 2012. It’s a household name, with 14 million people taking classes in 186 countries. It is fun, and joyful, and contagiously energetic. But behind the addictive routines, the tireless instructors, and the upbeat music is a compelling business model. Zumba makes money by licensing instructors and by keeping the instructors tied into the Zumba system. It also has a line of clothing that by Inc’s estimates is already a $100 million business and growing like a weed. And then there’s music: A Zumba CD just went platinum in France. This company is more than just fitness; it’s a lifestyle.

Can investors get a piece of it? We don’t know when this company might go public, but it will be interesting to watch if the three Albertos can keep the company growing. It’s hard not to root for a company that makes people so happy.