Interesting thread. A few things that tend to turn me off, at least from local club-type bands:
Co-owned band equipment or a "band kitty". ...that never seems to end well.
Bands that have no leader ("we all have an equal say") ...IME, that usually means there will be lots of time spent in debate over small matters.
Where "commitment" means you'd be expected to cancel an existing gig to take one of theirs (...uh, no, though I understand the desire).
Bands where certain members routinely avoid load-in, load-out chores, and it's never discussed and is "OK".
Any of these situations can probably work for some folks, just not for me.
One other reaction: I don't think it's a problem if a band asks me to show up at a gig to try out; it's actually a pretty convenient setting and a way to really feel out the reality of their working situation and musical & technical skills. ...even if the bass player on stage is leaving the band ...often the case.