Hmm, so this is pretty interesting behavior. Been noticing that AIM’s been giving me a system message that I’m signed on in different locations instead of kicking me off when I log in from multiple systems. It doesn’t have a jabber-like presence, but instead duplexes all incoming messages. Wackiness.

Ahh: AIM: Instant Message Routing

When you are signed in more than once, messages sent to you will be
delivered to all locations. You can control which locations will
receive messages by setting your Away Message.

When signed into multiple locations:

  • Your messages will generally be delivered to all locations not set as Away (or locations that have gone Idle).
     
  • If all locations are set Away, then messages will be delivered to all locations.

Please note, that you will only receive these notifications from the screen name AOL System Msg.