CBS Corp. bowed to public pressure and fired shock jock Don Imus on Thursday, walking away from its best-known radio personality and millions of dollars in advertising. Now, the media company must find a way to replace the sponsorship and recognition that Imus brought to a radio division that still has not recovered from losing Howard Stern to Sirius Satellite Radio Inc. last year. "They may be about to find themselves in a familiar, maybe worse, predicament. They had a year and a half to prepare for Howard Stern's departure and still could not find a viable replacement," said Holland Cooke, a news talk specialist with radio programming consultants McVay Media.Revenue from radio, the third-largest source for CBS after TV and outdoor advertising, fell 7 percent last year to $1.96 billion. CBS Radio will lose about $15 million in annual advertising and syndication fees it received from "Imus in the Morning," a source close to the show said. CBS had found itself in a difficult position since April 4, when Imus called members of the Rutgers University women's basketball team "nappy-headed hos" on his show -- remarks widely considered racist and sexist.