General Electric's (NYSE:GE) NBC TV network must be getting desperate.

The entertainment outfit announced earlier this week that -- hold onto your seats! -- Jay Leno, host of The Tonight Show, will retire and hand the show over to Conan O'Brien, whose own program, Late Night with Conan O'Brien, follows The Tonight Show.

Shocking, right? Don't worry; you'll have several years to come to grips with the news, because Leno won't actually retire until 2009. The question is: Why bother announcing such a nonevent? A likely answer is that NBC is hoping this gimmick will boost ratings, even if only temporarily, as the network celebrates The Tonight Show's 50th year this week.

Throughout much of the 1990s, NBC was a dominant player in network TV. Its sitcoms and dramas reliably delivered quality entertainment and commanded large audiences. But that time has passed. In the first week of the new fall TV season, Viacom's (NYSE:VIA) CBS ranked first among total viewers as well as among the key 18-to-49-year-old demographic that advertisers covet. NBC finished a fairly distant second, followed by Disney's (NYSE:DIS) ABC.

While all this may seem like a silly popularity contest, keep in mind that popularity and advertising spending go hand in hand. If NBC can't reclaim its lead, it will have trouble maintaining its long-standing record as the leader among the major networks in bringing in advertising dollars.

Ratings change from week to week, and NBC could recover. But what's truly dangerous for the network is that if it can't right the ship, its long-term reputation might suffer. Of the major networks, NBC once consistently captured younger viewers, while CBS, for a while, was derided as a station for old folks. Now the tables seem to be turning. The trouble is, once a reputation takes hold, it takes time to shake. For NBC, that should be reason enough to act fast.

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