Copied from AT&T's media Terms of service policy.
"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. Accordingly, AT&T reserves the right to (i) deny, disconnect, modify and/or terminate Service, without notice, to anyone it believes is using the Service in any manner prohibited or whose usage adversely impacts its wireless network or service levels or hinders access to its wireless network, including without limitation, after a significant period of inactivity or after sessions of excessive usage and (ii) otherwise protect its wireless network from harm, compromised capacity or degradation in performance, which may impact legitimate data flows."