Or....AT&T is just adjusting current plans. SMS and MMS services are limited by default with any carrier (or at least AT&T and Verizon). Once you go over, say, 200 of them, you get charged. AT&T is probably putting a stop to the MMS switch because, unless paid for, these features aren't free for unlimited use. iPhone plans didn't have this built in. If they don't have something to keep it in check (not to mention a legally written part of the service plan), then iPhone users will have an advantage over non-iPhone customers. AT&T isn't nickle & diming people, they're making everything even across the board. Granted, they should have had enough foresight to take care of this ahead of time due to the 3.0 software's release having been known for months now. I'll give you that one.
But all said, Marcus, write the news. Not speculations and opinions.