I touched up on this earlier when I was talking about the proper use of "brb."
It's so frustrating dealing with people online who don't know online etiquette. Crap like, "Don't put yourself on away if you're not away, use paragraphs, don't type in all caps, make sarcasm obvious through use of emoticons, proper use of emoticons" and stuff like that.
Most importantly, "DO NOT USE ONE WORD ANSWERS." Ugh, they're so annoying. If you ask someone to do something, and they reply "No," it's so frustrating, and it makes that person sound very rude! At least say something like, "No, sorry, I can't right now." Other one word replies are also really stupid. Elaborate, damn it. It's not like online convos should be that much different that real ones.
Seriously, I think a lot of people don't understand how to carry conversations on online. Ironically, I don't know how to carry good conversation in real life. Funny how that works...