I think I already mentioned one Salon article about Clear Channel, the US's national FM radio monopoly, but Plastic's music section points at a couple more under the banner, Clear Channel Sued By Denver Promoter Under Antitrust Law.
In addition to the Denver case brought by promotion co Nobody in Particular Presents, Clear Channel engaged in some wackiness sponsoring a Blink 182 event in Cincinatti. Will the FCC finally be forced to do something about increasingly homogenized radio?