I guess I have a short list of red flags, but they're just my point of view, I guess.
1. Drinking. A beer or two, okay. Crush a 5th in an hour and I probably wouldn't come back even if you invite me.
2. Drug use. If you want to, go right ahead. I just don't want to be around it.
3. Groups that overestimate their appeal or where they are going. If you're covering Mustang Sally and Folsom Prison Blues and insist you are "this close" to a record deal, it's probably not going to end well for anyone.
(If you're realistic and you know what you are, that's cool... I actually like playing those songs, you know, and cheesy cover bands are my preferred groups

)
4. If you don't have a consistent practice schedule, a developed setlist, or some sort of organization to the band (like a band leader), you're probably just a jam band. Which is perfectly fine. But recognize what you are and get the right people who have the same goals.
5. Bands that explain all their personal problems, one at a time, to you during an audition. Especially marital problems.
Some things that don't bother me;
1. Startup bands. Let's face it, every good band started somewhere, as did every good musician. But if you have a startup band, have a plan. If you do, you might be surprised at the people who like the chance to help build something.
2. Being asked to join at the end of the audition. That's how I got my current setup. The band had a bassist that left after two years and they were looking for a certain person to replace him and the criteria was not only playing ability, but various other things including age, physical appearance, attitude, etc. I was essentially a drop-in replacement for their old guy and I was offered the job at the end of my audition (which was 2 hours long, BTW....). So far, I'm really happy.
3. Bands that have been looking for someone for a while. It's not a big deal. If the reason is that they are looking for someone in particular with a certain set of skills, or certain criteria. It wouldn't scare me. And genre-specific bass players may be hard to find, depending on your area.
I guess that's all I can think of.