I just read his 'infamous' post. He explains that he got accepted, then found out he would have to change his cofounders for personal reasons. This concerned ycombinator, which changed its mind and decided not to fund him because of all the sudden changes and the fact that it was affectively a single-founder company.

http://joncrawford.com/post/20378314843/how-i-got-kicked-out...

It's even more complicated than that:

http://joncrawford.com/post/20378314843/how-i-got-kicked-out...

He glosses over it, but basically he appears to be a biz guy who had lost his technical cofounders for some reason and had his (idiosyncratic and evidently tenatative) acceptance rescinded.