Six weeks for closing a seed/angel investment from introduction to term sheet sign-off is not "too long". From my reading, it seems there was a firm commitment on both sides and hence, it was bad of both airbnb and YC to cut you off totally. At the very least, I would have expected the likes of YC to allow you to co-invest instead of simply assuming you were a newbie marine. After all, it was not as if YC had seen some stellar exits by mid-2008.