Sirius may be satellite radio, not Internet radio like Pandora—but it's still available over the Internet (in a way) on mobile via Sprint Power Vision and some other offerings, not to mention dedicated gadgets.

Either way, in the past, "Sirius has been criticized for adding lots of new subscribers unprofitably due to expensive content deals and promotions," Silicon Alley Insider blogger Michael Learmonth writes. "Now they've stopped and, well, the numbers show it."

In the past quarter, Sirius added just short of 280,000 subscribers, which pales in comparison to the 561,000 they added at this same time last year.

"But here's the very bad news: the vast majority of new subscribers— 89%—were people who just happened to buy a new car in the quarter with Sirius pre-installed," the report said. Now *that's* a problem, because usually car makers throw in a free year's worth of service, which most of these customers will probably not bother renewing.