What company is this? I cant seem to find it.
Unless the "stealth" part is the fact that they're a YC company. By that I mean that it could be a company/product that is well known but it's unknown that the company joined YC last summer. Though I'm not sure if a secret like that could be kept easily… (e.g. TurnTable.fm could fit the bill of some of the details: NY, music-based, Facebook API, game dynamics, crowdsourced content, VC-funded… but they're not part of YC AFAICT)
Another example is COLOURLovers which was big long before joining YCombinator. (so much so that I was very surprised that they did)
NB: if it turns out, I'm right about TurnTable.fm, remember that you've read it here first :)
Hence the ironic-quotes.
You do have an interesting theory though. Not that I totally understand why somebody would want to hide the fact that they're a YC alumni...