[aregsar]

"could it be that my interviewers have worked on SEO so much that it’s difficult for them to conceive of non-SEO related strategies for growing a user-base?" ...And from the rejection email "I encourage you to spend more time on figuring out customer acquisition (possibly through non-search channels)." So I don't think that "it’s difficult for them to conceive of non-SEO related strategies" is the reason, since they actually suggest the non-SEO strategy in their rejection email. I think that you need to view this from the perspective of ycombinator. The only investments for them that makes sense is a startup with high growth rate. (the very definition of a startup by PG). When you are playing the David against the Goliath of "Yelp" you can not compete on SEO. So you have to have an alternative DEFENSIBLE advantage to allow you to dominate your market. Another thing from what I have read over the years is that ycombinator looks for teams that are not married to their initial idea. In fact they prefer the team to the idea. So if in the interview you come off as very defensive about the validity of your idea that could be a red flag.