I disagree.
As months go by, it's going to be even harder for anyone to come up with a social network as big as FB. Why ? FB's critical mass!
As it's been said, all that differentiates Facebook for an individual user is the presence of that users friend’s on Facebook — which forces them to use Facebook to connect with them.
And this is precisely why FB is not a founding member of the OpenSocial foundation. Facebook is threatened by OpenSocial’s ultimate aim of connecting user profiles and enabling users to easily manage and port their data across any social network.
1) You can't just ignore YC's decision regarding your project, especially when you believe that your webapp will revolutionize the Web in some ways. These people are highly experienced profesionals:if you haven't caught their attention, get back to work because something key is missing.
2) YC is not like any other funding cycles... we are talking about mentorship here as opposed to financial back-up. Of course there are plenty of ways to raise money, but very few to get strong expertise.