I have this friend that lately has been IMing me, only to take a million years to respond to my IMs -- she'll say "Hi," and I'll say "Hi," and then like five minutes goes by without her saying anything -- meanwhile send a couple of IMs during that time just to make sure they're alive.

It's frustrating when the conversation is initiated by someone and then they don't keep up their side of the conversation -- why bother IMing me if you're too busy to have a conversation?