You won't have Howard Stern or any of his Wack Pack regulars to kick around on conventional radio anymore. Stern's last live broadcast of his notoriously popular morning show airs Friday through the syndicated network of Viacom's (NYSE:VIA) Infinity Broadcasting.

Folks who long for the outspoken radio star will hereafter have to turn to Sirius Satellite Radio (NASDAQ:SIRI), where Stern's camp will land with two channels of round-the-clock programming come Jan. 9.

Stern hasn't shied away from his role as a satellite radio pitchman since the $500 million five-year deal with Sirius was announced more than a year ago. The difference now is that he is going all out to make sure the migration leaves as few of his 12 million loyal listeners behind as possible. This week alone, he has appeared on everything from 60 Minutes to The Daily Show to The O'Reilly Factor. On Friday, he will host a live chat on Yahoo! (NASDAQ:YHOO).

Stern's future is clearly subscriber-based. Folks can buy a Sirius-enabled satellite radio and pay $12.95 a month for access to all of the Sirius programming, while videophiles can turn to In Demand for video content at $9.95 a month.

Even though XM Satellite Radio (NASDAQ:XMSR) is expected to close out the year with twice as many subscribers as Sirius, Stern's move is winning bigger headlines -- and even the larger market capitalization -- for the smaller provider.

XM's response, for now, has been surprisingly silent. There's only one Stern, but the fact that XM hasn't gone after Rush Limbaugh, Jon Stewart, Dr. Laura, Jim Rome, Don Imus, or Phil Hendrie is pretty baffling. Augmenting its Opie & Anthony offering with more popular shock jocks like Mancow or Bob and Tom has also failed to materialize.

Stern may never be a universal pleaser, but XM would be silly to let its lead squander. Bringing in folks like Snoop Dogg, David Bowie, and Bob Dylan isn't the solution. They are musical phenoms, but few radio listeners are willing to pay for what they actually have to say.

Viacom knew it couldn't replace Stern. To fill the programming void, it has contracted with both Adam Corolla and David Lee Roth, with the intention of carving up the Stern void geographically. Yes, Stern's loss will be a blow to companies such as Viacom and Clear Channel (NYSE:CCU), but XM had better wake up, or it, too, will get hit by the shrapnel.

Two months ago, XM was singled out as a recommended stock to Rule Breakers subscribers, and it's easy to see why. Satellite radio is far superior to terrestrial radio. Once you go "satrad," there's no turning back. And that's why XM had better make sure that Stern doesn't keep commanding the lion's share of media attention. I'm guessing that XM is simply biding its time. In a couple of weeks, Stern will be broadcasting for a significantly smaller audience than he commanded today, and the media circus will become more of a sideshow. If XM has a silver bullet to fire, let it happen in the latter half of January. Waiting any longer may be hazardous to its hold as the top dog in satellite radio.

Fools, now is the time to open your hearts and wallets to worthy causes! Please support our five Foolish charities at

Longtime Fool contributor Rick Munarriz is a Sirius subscriber, but he does not own shares in any of the companies mentioned in this story. T he Fool has a disclosure policy. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.