In what may end up being the shortest lived Terms of Service modifications we've witnessed, AT&T effectively banned and then unbanned some major data usage.
From the now rescinded AT&T TOS (emphasis ours):
This means, by way of example only, that checking email, surfing the Internet, downloading legally acquired songs, and/or visiting corporate intranets is permitted, but downloading movies using P2P file sharing services, customer initiated redirection of television or other video or audio signals via any technology from a fixed location to a mobile device, web broadcasting, and/or for the operation of servers, telemetry devices and/or Supervisory Control and Data Acquisition devices is prohibited. Furthermore, plans(unless specifically designated for tethering usage) cannot be used for any applications that tether the device (through use of, including without limitation, connection kits, other phone/PDA-to computer accessories, Bluetooth® or any other wireless technology) to Personal Computers (including without limitation, laptops), or other equipment for any purpose.
After re-evaluating the language changes (and probably fielding countless complaints and reading a couple of blog posts), AT&T has retracted the changes. By the end of the day, AT&T backpeddled at 3G speeds to make ammends.
In a statement delivered to Engadget.com and other internet news outlets, "The language added on March 30 to AT&T's wireless data service Terms and Conditions was done in error. It was brought to our attention and we have since removed it. We apologize for any inconvenience this may have caused."
So for now we all can breath a sigh of relief and continue to enjoy our mobile downloads.