When 2.0 came out last year, because apple's servers were swamped my o2 uk non iphone contract simplicity sim got activated through itunes when I updated to 2.0 because they couldn't validate it and since then it will activate any iphone (2g or 3g) I put it in after restoring to stock firmware.

I just updated my girlfriends 2g to 3.0, because she needs to use her sim in it I can't use my sim to activate because it will spot the sim change and won't work. The unlock is not available yet, so I thought I would try last years trick. She has a o2 pay as you go non iphone sim, after 3.0 restored on her iphone it wanted to activate with an apple id, which she doesn't have - I tried to create it a few times and it failed because apple's servers are swamped (it took 8 goes to download the firmware), in the end I thought I would try my id but when it tried it said we can't authorise apple id's at the moment please create an itunes account later - and then activated the iphone! I tried restoring another 2g using her sim, and at the end it activated straight away no sweat with her non iphone pay as you go sim.

So if you have an official iphone carrier but aren't on the iphone contract, there is a good chance you could update to 3.0 and get your sim linked as official because of Apple's swamped servers. I don't know, but doubt very much if it will work with non iphone carriers, and I can't guarantee it will work for you (I had a spare for her if it went wrong and I had to wait for Jailbreak) so don't try if your iphone is your only phone, because you could be locked out until a jailbreak is released, but if this is like my sim from 2.0 once it does it any firware will activate with the sim (ie my non iphone plan o2 sim I managed to get passed on my 2g when 2.0 came out activated 3.0gm on a 16gb iphone 3g no problem, and has done all firmwares with a few different 2g iphones no problem)