[TeMPOraL]

Exactly this. Some people seem to think that using smartphone means doing something irrelevant, less important than talking to a person. But you know what? On the other side of that phone there usually is a person.

One of the rudest behavior I encounter is people suddenly coming to you and interrupting in the middle of your IM conversation, demanding undivided attention and refusing to accept that you're in the middle of a conversation. IM is not e-mail, it's often as time-sensitive as voice, and quite often that IM conversation is much more important than whatever the interrupter came with.