I am at my parent's place right now and apparently I left my laptop on and logged into AIM at my apartment.  When I logged in here (at my parent's house) I was sent to a page with this on it:

Instant Message Routing

The instant message you received was sent to notify you that your screen name is currently signed into the AOL Instant Messaging Network more than once. This can occur if you log onto AIM and AOL on the same PC. This message is sent to help you manage your instant messaging sessions across PC-based and wireless clients.

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.

AOL will never ask you for your password via Instant Message.

 

The coolest thing about this is that the feature does not require you to be using AOL's software.  I am using Trillian on my laptop and Gaim at my parent's house.