I was unaware of any connection to Rush Limbaugh. I don't listen to him, or Howard Stern. But I did see this item yesterday:
"On Tuesday, Sen. Sam Brownback (R-Kan.) wrote to Viacom president Mel Karmazin about Infinity's lack of action. "In light of Infinity's reported new indecency policy, and the supposed use of a substantial time delay, I do not understand how such a broadcast could be aired using an Infinity broadcast license," he wrote.
Stern said he expected Infinity to be forced to drop him by the threat of huge fines (Congress is considering raising fines for broadcast indecency to $500,000, up from the current maximum of $27,500) and possible loss of broadcast licenses."
I can't help to read that as a threat to censor, while the timing of the event is what leads me to wonder about the real reason for the action.