Some AT&T iPhone 3Gs's have working MMS and tethering

AT&T in the US were not meant to be offering tethering and MMS at launch for 'system upgrade' reasons.

From Engadget

Update: Turns out the secret to enabling MMS and tethering lies buried in the carrier settings file, which happens to be the same black magic employed to roll out 3G MicroCell support a while back. Customer devices are at AT&T 4.0, but there's an AT&T 5.0 profile floating around the interwebs that turns the features on -- it's just a matter of finding it, installing it, and making sure that your account is provisioned for multimedia messaging. Thanks, everyone!

O2 MMS service for iPhone turned on then turned off

Not sure what's going on with O2's MMS for iPhone. A friend of mine who updated to 3.0 today tried activating by sending a text to 1010 and got the reply that it wasn't up and running yet, although I am still able to use the service, which I set up yesterday - see screenshot. The weird and wonderful world of O2