iPhone MMS on AT&T showing incorrect sender number? (poll)

It all started with an iPhone-borne MMS video of a Kirby plush toy that I tried to send. You see, I don't have a 510 number -- that AT&T mobile number belongs to a friendly gentleman living in Fremont, CA, about 40 miles from where I reside -- but that didn't stop the message from going through the airwaves with his number listed as sender. Confused? Yeah, so are we, and a quick look through various forums say we're not alone. We've contacted AT&T for more information, but in the meantime, let us know if you've noticed any similar problems.
Read - MMS coming from wrong sending address?
Read - MMS messages I send showing received from different phone number iPhone