[ovi256]

You should read http://www.paulgraham.com/swan.html

Most startup ideas are non-obvious in their very early phase. If there was already proof one way or another that they were good or bad, they would be already done, or already dropped, respectively.

Also, the founders have much more knowledge about their startup. You have what you got from that one paragraph description you read. That's a huge asymmetry of information.

PG's essay explicitly calls us out:

"At YC we're excited when we meet startups working on things that we could imagine know-it-alls on forums dismissing as toys. To us that's positive evidence an idea is good."