From Boing Boing, AT&T's new terms of service allow them to cancel your service if you criticize them. Under § 5.1, "Suspension and Termination":

Your Service may be suspended or terminated if your payment is past due and such condition continues un-remedied for thirty (30) days. In addition, AT&T may immediately terminate or suspend all or a portion of your Service, any Member ID, electronic mail address, IP address, Universal Resource Locator or domain name used by you, without notice, for conduct that AT&T believes [...] (c) tends to damage the name or reputation of AT&T, or its parents, affiliates and subsidiaries [emphasis mine].

Outraged? You should be. But AT&T, as a private company, isn't bound to honor the First Amendment; that affects only the government. However, as a "common carrier," AT&T may be bound by 47 U.S.C. 202(a), which prevents common carriers from making

any unjust or unreasonable discrimination in charges, practices, classifications, regulations, facilities, or services for or in connection with like communication service, directly or indirectly, by any means or device, or to make or give any undue or unreasonable preference or advantage to any particular person, class of persons, or locality, or to subject any particular person, class of persons, or locality to any undue or unreasonable prejudice or disadvantage.

It sounds like AT&T's refusal to permit customers to criticize it constitutes "discrimination in practices." Any lawyers out there?