I was so annoyed by those that I started trying to return them to the sender. What I didn't know is that "standard mail" (the bulk rate) doesn't include return postage in case the recipient doesn't want the item or there's a mistake with the item. So the post office most likely just discarded them and never sent them back to AOL.

Nowadays when I get junk mail I put a first-class stamp on it before attempting to bounce it back to the sender. Theoretically this should work, although there's no guarantee the postal workers will cooperate.