We look at the founders, if that counts as real world data. We don't look at much else.

No one cares about the idea. In fact we applied with a different idea to snaptalent but it was the team that mattered.

We could change our idea again and be confident of smashing it out the park because our team is super solid, motivated and hell bent on success.

Isn't that risky? After all, it matters to you whether you are pursuing your own idea. If not, then it's like working for someone else.

So if you can change your idea at any time (or are encouraged to do so), how do you know it would change to something that you have contributed to? Isn't an idea change likely to break up the group?

You've misinterpreted his comment. YC doesn't tell founders what to work on. No one is going to pg and saying, "OK, you said our idea sucks, so what do we work on now?" Instead, pg says, "Your idea sucks." And the founders either say, "We disagree, but why do you think so?" or "Yeah, we noticed. We're thinking about switching to this...what do you think?"

In fact, pg is very likely to think your idea sucks at some point in the process. I still think he's a little iffy about ours over a year later.

I think Sequoia Capital has some decent guidelines for what to look for: http://sequoiacap.com/ideas/ However, if you were to ask Marc Andreessen the only thing that matters is the market: http://blog.pmarca.com/2007/06/the-pmarca-gu-2.html -- according to Marc, the team doesn't have to be superstars, they just have to be "good enough"

The question every investor would like asked is how to distinguish good startups from bad. I think most collect hueristics applied to a few numbers and gut feelings.

Founders seem to not get along? Seem not passionate enough? Market too small? Market too hard to win? Not builders?

All lame.

Persistence, vision, and flexibility are things I've repeatedly heard help predict winners.

In the sense that the YC folks explicitly state their hypotheses and have publicly revised some of their guidelines in light of experience (e.g. stressing need for teams, adjusting minimum age range upward) it's more scientific than most of what other VC's disclose.

The things that usually bring down startups tend to be team related. Even though having a good idea is important it's not as critical. By focusing on the team YC is attempting to combat what is most likely to hinder success.

I believe YC uses the same criteria that Walmart uses to select its suppliers and vendors. Or maybe CostCo!!!