In addition to blocking calls, at&t is suing 2 Rural LECs in Iowa for exorbitant fees and abusing the system. [dslreports] I guess it is okay for at&t to screw people and the system, but not for anyone esle. Ever hear of inter-carrier compensation, Whitacre?? (This was post 3/27/07).
UPDATE (May 3, 2007): FCC Chair K-Mart finally says you can't block calls. [GigaOm]