I do think as a generalisation there's a big difference between an every man for himself challenge, and something reciprocal, or where you're part of a team. In that sort of situation I think dropping out without notice is a big deal. That said, this is a small fandom and you're right that we don't seem to have a list of repeat offenders (and I have been in fandoms where that was definitely the case!) so I'm happy to roll with it.