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.
Is your iPhone MMS sending via a different number?
Yes, and it's led to some very awkward exchanges.2873 (14.2%)
Nope -- not yet, at least.6296 (31.1%)
Why bother with MMS when you have a data plan and email?2599 (12.8%)
I don't have an iPhone or an opinion, I just like pushing buttons!8463 (41.8%)

Read - MMS coming from wrong sending address?
Read - MMS messages I send showing received from different phone number iPhone

HTC HD2 turns up in purported T-Mobile USA materials