Which companies should Yahoo acquire next? What's the secret to a successful start-up ecosystem in New York city? When is Facebook stock worth the buy?

These were just a few of the big questions discussed this morning at TechCrunch Disrupt in Manhattan's Pier 94, a cavernous former ship terminal (complete with draft and sparrows flying overhead) that functions this week as the event's home.

Monday's panels and presentations consisted of a veritable who's-who of the tech and start-up world—with a big focus on the growing New York City start-up scene. On the investment side, Fred Wilson and David Tisch chatted about Facebook's IPO and New York City innovation. Jason Goldberg, the founder of Fab.com, said he wants to create the next Ikea—not just the next Zappos-sized company. Michael Arrington said he'll be buying Facebook stock today. And Brad Garlinghouse, a former executive at AOL, admitted to hearing rumors that Arianna Huffington was almost fired from The Huffington Post.

By lunchtime, more than a dozen investors and entrepreneurs presented to the crowd. Here are a few big ideas that came out of what they said on TechCrunch Disrupt 2012's first day.

New York City needs more exits. Whether or not you believe "Silicon Valley" can compete with San Francisco as a start-up hub, one thing is for sure: "New York City needs more big, big exits," says David Tisch, managing director of TechStars, a start-up accelerator program. "And I believe you'll be seeing them in the next year." (As for the name, "Silicon Alley," Alexis Ohanian, one of the co-founders of Reddit who now serves as East Coast ambassador for start-up incubator Y Combinator, begged the audience to come up with a better moniker. "No one even calls it that!" he said.)

Gilt probably knows you better than you do. Alexis Maybank, co-founder of Gilt Groupe, understands customization. By analyzing user click data, she said Gilt generates more than 3,000 personalized e-mails every day. The message: Understand your customer and direct the right products to the right people.

Military-inspired innovation rules. Tom Katis enlisted in the military twice. The first time he enlisted was after high school, and he moved to San Francisco when he completed his tour. Then, 9/11 happened. Katis re-enlisted, this time serving two years in Afghanistan from 2002 to 2003. Facing heavy combat, he grew impatient with the military's outdated communication system. So when he left the military, he dove into the tech start-up world, and started Voxer, a consumer-driven walkie-talkie app.

Dropbox and Box seem overvalued (says the CEO of YouSendIt). Brad Garlinghouse, the new CEO of YouSendIt, says his company is earning $40 million in revenue and is nearing profitability. YouSendIt has flown under the radar compared to companies like Dropbox, which has been valued at $4 billion, and Box at more than $600 million.  But he urges his competitors, Drew Houston (Dropbox) and Aaron Levie (founder of Box) to be more transparent about their revenue figures.

Tumblr had a scaling problem. Last year, Tumblr had 15 employees. Today, it has more than 105. "I was convinced with this scrappy little team we could get to a certain point," said Tumblr's 25-year-old CEO, David Karp. "But we got ourselves into a nasty nine months where we were behind on our work. We're mostly caught up now."

Yahoo should think about a couple acquisitions. "Can Yahoo be saved?" Brad Garlinghouse, a former Yahoo executive pondered out loud. "I think the answer is yes." But, he admits, the company will need to go an aggressive buying spree to remain relevant. First, they should buy Flipboard, a social news magazine. Then, they should buy Gravity, a start-up that personalizes websites based on user interests.