Sirius Satellite Radio (NASDAQ:SIRI) hasn't gone wanting for buzz over the past year, thanks to the signing of the King of All Media, Howard Stern. And as Sirius watchers well know, the Stern factor has translated into a surge of subscribers: More than a third of its subscribers at the end of 2005 came on board in the fourth quarter alone. Sirius has to be careful, though, that it doesn't kill the goose that lays the golden eggs.

It's a sure thing the great Stern migration will continue, but it probably will be at a somewhat slower pace than that of the fourth quarter. With Stern now in place, Sirius investors might well be asking themselves: What's the next step for bolstering revenue?

A recent article in the USA Today provides some possible answers. The piece notes that both Sirius and rival XM Satellite Radio (NASDAQ:XMSR) have a variety of other revenue sources that they can mine. Among the available fonts of cash are ad sales, premium data services, and distribution of content over other channels. All of these seem to be reasonable avenues over the long term to fuel growth; however, Sirius should think twice about pumping up advertising too much in the near term.

In the case of advertising, Sirius' dependence on Stern is something of a liability. While XM's 6-million-plus users likely signed up for its service for a wide variety of reasons and consequently tune in to a number of different channels, probably more than a third of Sirius subscribers came just for Stern. So advertisers naturally will seek to have their ads played on Stern's channels.

However, immediately placing more spots on the Stern show could turn out to be a big mistake. I've been listening for only a couple of weeks now, and I've already heard one caller complain about the (very few) commercials on the show and the fact that Stern doesn't always do a Friday broadcast. Stern fans tend to be rabid about getting as much Howard as possible, and if the ads increase too much too soon, some may well feel betrayed and drop their subscriptions. And if Sirius starts to lose Stern fans, it stands little chance of thriving.

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Fool contributor Brian Gorman is a freelance writer in Chicago. He does not own shares of any companies mentioned in this article