Many of the companies who apply to YC have this much traction... There's certainly a TON of benefit to be had from YC at their current stage.

That's my question -- would YC make the offer now, and would the company accept it? Basically, could there possibly be a re-do? The answer might be "no" for both, but it might be "yes". Is applying to YC and accepting a one-shot deal for all parties, or can there ever be a chance to get back together? From the responses and posts, it looks like it's a one-shot deal - either they accept you and you accept the offer, or there's no chance to get together again in the future.