I just read through the RFS (http://ycombinator.com/rfs.html), which was written in 2009. I'm not sure if YC is still looking for those types of products. More specifically, there's an item that says "Things built on Twitter".<p>Recently every investor I talked to didn't like products that are built on top of Twitter, and I wonder if YC's perspective has also changed.
I'm one of the founders of Crowdbooster, a YC S10 company built on Twitter.<p>Twitter, and specifically the API team, has worked hard to come up with guidance for where they think there are opportunities in the ecosystem.<p>They have very clearly told third-party developers to stop making Twitter clients [1]. Twitter wants to own the display of tweets since they are focused on making advertising their core business.<p>But there are definitely opportunities if you think beyond just making clients. The five main categories that Twitter specifically mentions are: Analytics, Curation, Content, Publishing, and Enterprise [2].<p>To echo PG, there are definitely still big companies to be built on top of Twitter. You just have to think big to begin with.<p>[1] <a href="https://groups.google.com/forum/#!topic/twitter-development-talk/yCzVnHqHIWo" rel="nofollow">https://groups.google.com/forum/#!topic/twitter-development-...</a><p>[2] <a href="https://dev.twitter.com/blog/ecosystem-showcase" rel="nofollow">https://dev.twitter.com/blog/ecosystem-showcase</a>
It has been updated since the iPad was not released till 2010 and there is an RFS: <a href="http://ycombinator.com/rfs6.html" rel="nofollow">http://ycombinator.com/rfs6.html</a>