Every team works on an idea. A lot of the last batch are underwhelming:
http://www.techcrunch.com/2008/03/14/y-combinator-demo-day-r...
> AT Interview stage, from one application form how familiar do you expect someone to be once you've read 500 forms
If they're flying you in for an interview you're no longer in the pool of 500 forms. If they are asking questions that make it clear they aren't paying attention to the information you've already given them it just goes to show that your grandiose plans are fairly inconsequential to them and they're only tossing their spare change at you.
> Some companies like rescuetime and heroku were well past the idea stage
Companies that have a lot done already are the ones that are going to run into the mismatch I talked about. Here's this great thing you made; now you're giving ownership to people who don't feel about it the same way. There's not a lot of investment of money, time, or emotion on the part of YC. So it seems to me that the exchange is equity for exposure -- basically you've started off your marketing budget at the 6% that YC takes.