if you have the setting ON, then you will be signed out of AIM when you exit the App (ie, press the Home button of the iPhone)..
So yes, you won't receive any messages as you are signed out...
Jumping in with a question. We're trying to test Aim with each other and each get the error "Unable to send IM - Your message was blocked from being sent by *****".
I cannot figure out why this is happening or how to fix it. Anyone know? Thx.