I know that XM wouldn't have taken this decision lightly. In fact, it was probably the very last thing they wanted to do....but, the word is out that they have begun planning to put commercials on four of their programming channels.
Now, if I'm going to have to pay as much as $11.87 a month to get your service, as well as pay to get a special receiver, why in the world would I want to do it if the product is the same as I can get for free just by turning on the radio. The irony of this is that the four channels are programmed by Clear Channel--the gigantic company that is also programming most of the radio stations in the country. So, now on these four channels at least, the MUSIC sounds the same (most likely) as what you can get via broadcast and the COMMERCIALS are there as well.
I'm also not sure that this is a good idea for Clear Channel, either. They have wanted to separate themselves from the concept of commercial clutter for about 18 months. Something I've been interested in as a researcher. So, even though it's only people in the industry who will know that on these four XM channels it's CC that's loading them with commercials...that's an image I wouldn't think they'd want to send out there.