Sarah McBride at the Wall Street Journal gives us a little more insight into the commercials returning to 4 XM channels.

The dispute arose in early 2004, when XM decided to make its music channels commercial free. Previously, XM had run small amounts of advertising. Clear Channel, which provides XM with talk programming as well as music programming, wanted to stick with the commercials. The companies entered arbitration, with a panel ultimately deciding in favor of Clear Channel regarding its right to provide commercials on Clear Channel-programmed stations.

 (My advice to XM: add some wacky DJs to the channels and call it an "Entertainment" insead.)