They're losing income because of:
1) The economy. Until it recovers, people don't have the disposable income they once did. I'd bet that with all of the people who are cutting back on things, their extra subscriptions are probably one of the first to go. They may have had a radio for the car and a seperate one for the office. Now, they may just have one in the office that they take back and forth.
2) P2P and illegal broadcasting. People may think they're doing a good thing by uploading the content, but really, they're hurting the company. If someone can get the show for free online, then what incentive is there to subscribe? For every person that downloads off the internet, that's at least $12.95 a month that SiriusXM is missing out on.
3) The car dealerships going under. Sirius counts subscriptions before the car is actually sold, right? Well, if the car companies are making less cars, then that's fewer subscriptions, but more honesty in their counting.
If i'm a sports team and I announce my attendance as "tickets distributed", then I could announce 67,210. In reality, maybe only 57,810 people show up to that game.
OTOH, if the car dealership failures force SiriusXM to be a little more honest with announcing subscriber counts, that could help the company in the long term. Suppose Sirius has 12 million individual subscribers, but a total of 18 million active radios, with an additional 3 million cars unsold. Would the investors be happier hearing 12 million subscribers, 18 million subscribers, or 21 million subscribers?
4) Call me crazy, but I don't think the music (playlists, dj's) has anything to do with it. If you subscribe for any of the talk or sports, they still count you just the same.