IIRC, AOL got whacked by a court years ago because they censored some chat rooms and not others. The court held that since they censored some content, they lost their status as a common carrier and were liable for other content they didn't censor (either by intent or mistake). This was a particularly interesting case, since the implication was that ISPs who _don't_ censor content _are_ common carriers, which I don't think has otherwise been touched upon in the US.
I would be most interested in a citation of this alleged case. Perhaps you are thinking of the Stratton Oakmont case in which a New York court found Prodigy liable for for postings in some of their online fora. Since there is a section in the 1996 CDA specifically to reverse the outcome of this case, anyone who cites this case as relevant to the current situation in the US is just plain wrong. Also, ISPs in the United States are not common carriers. Even the ISPs that are owned by phone companies (which are common carriers for their phone service) are not common carriers. Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Information Superhighwayman wanna-be, http://www.johnlevine.com, ex-Mayor "More Wiener schnitzel, please", said Tom, revealingly.