It can be hard to adjust to someone who has a casual online chatting style. I accept this from some of my friends because it just feels ok, but I get annoyed when others seem to drop me in the middle of a conversation. Maybe its because I'm older and growing up there never was a way of communicating where it was simply OK to stop communication without saying goodbye, talk to you later, etc. So to me, it just seems rude, but since this is just how everyone is, I know I need to adjust. On the flip side, those who are this casual aren't all that serious. It really can be a litmus test for deciding who is a good friend, etc and who is just someone you know casually.