Cellphone carriers allowing cross-carrier photo swaps

So it looks like cellphone carriers have finally gotten hip to the fact that nobody really cares what carrier their friends are on — they just want to send MMS messages to them without restrictions. Despite the fact that they all witnessed SMS taking off after interoperability was established, for some reason it took them this long to realize it would likely be the same story with MMS — maybe because 'S' and 'M' are different letters, these things are not so obvious? Yeah, we know the technical reality of this implementation is non-trivial, but what do you want? If you build a service inside a walled garden, they will not come. Anywho — Cingular and Verizon have quietly implemented interoperability of MMS, so perhaps the rest of the carrier crew will wise up in the not-too-distant future, as well.