This is a less-then-subtle attack on network neutrality. Service providers (including, in this case, wireless network providers) keep confusing providing the network and providing content. Everything that happens on the application layer is, frankly, none of their business. Besides, if they begin attacking p2p users systematically, all they're going to do is force the next generation of software to encrypt its traffic.
From IP Democracy:
AT&T will jettison wireless users that engage in P2P file-sharing over its network, the company said Friday in a letter PDF filed at the FCC (and flagged today by Ted Hearn at Multichannel News). Senior lobbyist Robert Quinn answered a question posed at hearing last week by Republican FCC Commissioner Robert McDowell about the company's policies of managing P2P network traffic on its broadband wireless platform.
uinn said that AT&T's terms of service (as well as the TOS for most other carriers) bars the use of P2P applications on the wireless platform. "Use of a P2P file sharing application would constitute a material breach of contract for which the user's service could be terminated," he said. [From IP Democracy]