I have a theory that when I send someone a pm they appear to log off. I'm not convinced they do really, they just seem to disappear from the list for a few minutes.
I was feeling a bit paranoid that everyone I wanted to speak to was hiding, but I'm starting to see a pattern.
I just sent a pm to red jimmy, but he disappeared, so I went in and deleted it (still in my outbox as he hadn't read it.... then he replied to it....very weird)
Edit: just went back to check the message hadn't been sent, and it was in both my outbox and sentbox
LATaylor kept disappearing the other night, but said she hadn't gone anywhere ....weird.