Just took this from Aweber's site and think it's a good policy as it protects your list:
When a complaint is made by a subscriber, AWeber automatically removes them from your list.
No future email messages will be sent to them from the list they complained about, eliminating the possibility of future complaints from the same email address. In turn, this protects your email lists.
Since this is both the most appropriate and only effective action to take, and because additional actions taken can cause further issues, the identity of the complaining subscribers is not provided.
The link if you'd prefer to read it from the source: How Do I See Who Complained? :: AWeber Knowledge Base
Just letting y'll know if you didn't already.