What I think AOL is doing, essentially, is threatening to block business email unless they pay a fee. If they pay a fee, their mail bypasses spam filters. Now there's a revenue stream I'll bet you haven't thought of. Set up a spam filter. Charge people to have their mailbox protected from thousands of annoying spam messages (part of the package of your membership in AOL. Then charge companies to put their mail through anyway.
This idea is even more brilliant than they imagine. In a few years, after you are once again deluged with unwanted e-mail, they can start offering a new service to the user: we will block the unwanted e-mail that we used to filter for an additional monthly fee. But you thought you were paying an additional monthly fee already? That's like the cable fee you used to pay for commercial-free specialty channels, which are you still paying for, and which now have commercials.