AT&T has just announced that MMS -- a much-ballyhooed feature of iPhone OS 3.0 -- will finally be hitting AT&T on September 25. There's still no date for tethering, though the company is holding the line that it'll be offered "in the future." Expanding on the logic behind the tethering delay, they're saying that "by its nature, this function could exponentially increase traffic on the network, and we need to ensure that some of our current upgrades are in place before we can deliver the expanded functionality with the excellent performance that customers expect." We're no network engineers, but "exponentially increase traffic" and "AT&T" are two things we don't typically like to hear in the same sentence -- let's hope the 850MHz, 7.2Mbps, and backhaul upgrades they're cranking on right now go a long way toward sorting that out. As for MMS, they're acknowledging that the release "does indeed fall a few days past the official end of summer," arguing that their support of more iPhone customers than any other carrier in the world made a positive launch experience a bit of a challenge. Of course, virtually every other phone AT&T sells (and has sold for the past several years) supports the same tech, so this feels like a pretty active admission that iPhone users blaze through data-rich features at a pace that the carrier has been ill-equipped to handle.