AT&T has defined their official throttling policy for smartphone users on “Unlimited” rate plans. Turns out, unlimited really doesn’t mean unlimited, if you’re AT&T.

Smartphone users on a regular 3G device will start experiencing slower device speeds as they use more than 3GB of bandwidth in a month. Folks using a 4G LTE device will hit that cap a little later, at 5GB of bandwidth. Ironic, as I didn’t think that AT&T offered unlimited data plans when 4G devices came out - but I could be wrong on that point.

I rarely use more than 2GB in a month, so this isn’t a huge issue for me - but it does bother me. I’d like to know exactly HOW slow they plan on throttling people who bust the usage cap. What speeds can those people expect? 7MBit/sec? 3Mbit/sec? 1Mbit/sec? Or are they going to slam you into the internment camp of EDGE at its craptacular 160Kbit/sec? That remains undefined by AT&T. The fact that they are putting a limit on something unlimited bothers me as well… but I suspect that’s going to be a battle that us consumers will ultimately lose.

Thanks to TUAW and Boy Genius Report for breaking the news. If you’re not reading either site, give them a look.