The 1 key thing star founders and CEOs say catapulted their startups into major success

Rascoff: We said: "Let's try to figure out what every house in the country is worth. How do we do that?" Most of this information — bed, bath, square footage, tax assessment, sale history — is available in county courthouses, but we had to go acquire it, digitize it, and then build the data layer, the Zestimate, that sits on top of that.

And when we launched in, I think it was February 2006. We got about a million visitors within the first day. I still don't think any other service — Snapchat, Facebook, whatever — I don't think anyone else has had a million users in day one. Because it's so cool and so innovative to say, "Oh, my god, I can grab my kid's school roster and I can Zillow everybody at my kid's school and see what everyone's house is worth, see what everyone paid for the home." That was just, like, this, "Oh, my God" kind of thing that launched the company in 2006.

Rad: Justin's younger brother was throwing a birthday party for his best friend at USC, and he had a bus going from USC to his parents' home. The bus was going back and forth, so a total of about 500 students. Justin called me one day and said, "Let's pay for the bus and call this a Tinder party." So we paid for the bus and put a bouncer at the door and told every student that they couldn't walk in unless they downloaded Tinder. You'd literally have to show Tinder on your phone. So about 400 people downloaded Tinder at USC. They went home and opened the app and started matching with each other. It really created a phenomenon within USC.

Immediately after that, every afternoon the whole team would leave the office, get in a car, and we would drive by every fraternity and sorority in Los Angeles, then San Diego, then Orange County, and every school we could cover.

In the beginning of January we had about 20,000 users, and at the end of January we had 500,000 users, all organic. The growth curve was unimaginable. It was pretty amazing.

Weisberg: We emailed every news anchor out there. We were like, "We're former NBC-ers, thought you would love this, thought you would appreciate the need that we're solving." Hoda Kotb responded, and she said, "I'll check it out!" We didn't know her. We followed up with her two more times, but got no response. Day four of us in business, she said we were one of her favorite things — on air — and it totally changed our life.

We went from, at that point, let's say, under 1,000 users to thousands. All of a sudden, we had geographic diversity. And all of a sudden, we had huge pockets of the country paying attention to what we were doing.

Shontell: Wow. What does a Hoda bump do to your newsletter subscribers?

Zakin: It crashed our site. It crashed our email inbox. We got a few thousand people from it. It was life-changing.

Levchin: I started noticing that people were transacting through Paypal. Then I got an email from someone saying, "Hey, do you have a logo? I need a logo, ideally scaled down so I can embed it in my eBay auction posting." And up until that point, I had a really peripheral understanding of how eBay worked and what it did, so I looked it up and thought, "Oh, my God — this is like a den of illicit commerce. I need to block them from touching my product."

At some point, Peter Thiel asked me, "What are you spending your time on?" I said, "There's this eBay user; they're just trying to use our product like crazy. They're like cockroaches; you try to block them off and they keep on coming in through a different entrance."

He said, "I think that's what they call market pull. I think all these people trying to pay online, they don't have any better choice than your haphazardly put together demo." And so the last pivot of Paypal was pulled into its final shape by the eBay public.

Houston: We made a demo video for Dropbox. That was how we got our first couple hundred thousand users. But what ended up really working was we had this incentive referral program, so that if I invited you to Dropbox, you would get some free space, I'd get some free space. So that two-sided incentive and kind of gamifying ended up making something that was otherwise a single-player utility into something people used for sharing, that spread virally.

Corcoran: And I looked and looked and looked at the New York Times ads and saw there were hundreds and hundreds "One bedroom 320 month," "One bedroom 330 a month," "Doorman one bedroom: 340 a month," and they all looked alike. And so I went back and said, "Could you build a half wall between the L and the living room so I could advertise as 'One bedroom and den?'" So that Sunday, my ad went in even before the wall was built, "1 BR Plus Den: 340." It fit on one line, right margin, and I probably got 80 phone calls that next morning.

Blumenthal: The fashion director at GQ calls us up and is, like, "Guys, the magazine's going to hit newsstands any day now — where is the website?"

We were going to be in the March issues of GQ, and it was February. We thought, "Oh, we have a whole month." Just to show you our naiveté, it was like, "No, the March issues comes out in February." We literally scrambled, got the website up. We ended up hitting our first-year sales targets in three weeks — sold out of our top 15 styles, had a wait list of over 20,000 people.

It was mayhem and the question is, "How do we maintain that momentum?" When we got those features in Vogue and GQ, it was literally that moment that the business took off. I think founders and CEOs often take credit for being the smartest people in the world, but so much is serendipity and timing.