Very interesting topic. I must say, I have to agree with a few of the things said above. Here's my list.
1. Bio-less group biographies- Whether it's any at all, I'd really appreciate a biography for the group. Maybe the group's just starting out, and they're really new, but if I've been in a roleplay for a month and they still haven't scrapped together some sort of pre-school essay, I might conjure an uneasy feeling.
2. Popular Roleplays with Popular Websites- I know a lot of people who like to be in big, active, complexly-plotted roleplays with an equally complicated website. This is not for me. I do enjoy roleplays with complex storylines, but when the group leaders require you to go onto the website daily and do whatever stuff they want done online, it simply becomes too much for me. I joined a Warrior Cat roleplay with over 45 members, and I had no idea what I was getting myself into. I went on their website, and I knew that there was no possible way I could survive a day in that Clan.
3. People Accepted for Not Being Accepted. I know a few times where I've had to submit an rp sample to the group leader, and whether I was what they were looking for or not, I've been turned away. I've been told I wasn't "literate" enough before, and I easily understood their perspective- I wasn't complaining. But what bothers me is when I see another player ask to join, and the group leader doesn't even ask for a roleplay sample. They just let them join without doing anything at all...and after all my hard work at that roleplay sample...
Also, when they beg and beg to be let into the group, and the leader gets fed up with their whining and complaining, so they just let them in...
4. I have to admit, wolfspeakers and text talk turns me off.
5. Power-playing.
6. The "I-Consider-Myself-Of-Higher-Quality-Because-I've-Been-In-The-Group-Longer-Than-You-Have."
7. When the group leader requires a roleplay sample, but will let anyone in no matter how well of a job they did. This bothers me simply because some people work hard in order to be accepted into a roleplay. It's not that I'm saying nobody wants to work hard to be in a roleplay, but if the leader is going to accept anyone who wants to join, then what's the point of an rp sample? This also waves a red flag because it says, "Hey, this person might not care about my hard-working, roleplay ethic."
That's all I can think of...for now.