I basically agree with Jonah Goldberg's point about the limits of the Limbaugh-Oprah comparison, which is one reason my original post circled around to a Rush-Jon Stewart analogy instead. But I think he's missing the point with this:
Why, for instance, is Limbaugh less serious a spokesperson for a point of view than, say, Keith Olbermann or, for that matter, Bill Moyers? Olbermann, who started out as a sportscaster, says things his ideological opponents don't like into a TV camera. Limbaugh says things his ideological opponents don't like into a radio microphone. Limbaugh's more successful at it. Again, I think people look foolish when they are starstruck -- particularly starstruck in large crowds -- about anybody. But, I'm not sure that the adjective "entertainer" takes you very far analytically here at all.
But look - the point of calling Rush an entertainer isn't to say that nobody should ever listen to him or care about what he has to say. The point is that by virtue of being an entertainer, and having the incentives of an entertainer, he's a poor candidate to fill the role of spokesman (and ideological enforcer) for the conservative opposition - a role that he seems eager to take on, and that Barack Obama is very eager to see him occupy. I don't think Limbaugh is a less serious voice for conservatism than Keith Olbermann is for liberalism. But that's because I don't think either of them should be taken all that seriously - because they're media personalities whose primary loyalty is to their image and their audience, and whose primary purpose is to provoke and get attention. And I think it should go without saying that American liberalism would be in serious, serious trouble if someone like Olbermann were occupying the kind of role on the left-of-center that Limbaugh seems to be shouldering his way into at the moment.
Just imagine, for a moment, how conservatives would react if four months after the worst defeat liberalism had suffered in a generation, an Olbermann (or a Moyers or a Michael Moore or a Bill Maher or whomever) showed up to deliver the keynote address at a liberal equivalent of CPAC, and during the course of his speech he blasted every Democrat who disagrees with him as a miserable sell-out, suggested that conservatives are fascists and conservatism a psychosis, lectured the crowd on the irrelevance of policy ideas to liberalism's political prospects, and insisted that the only blueprint liberals need to win elections is the one that Lyndon Johnson used to rout Barry Goldwater. And then further imagine that both before and after this speech, a series of left-of-center politicians ventured criticisms of Olbermann, only to beat a hasty and apologetic retreat as soon as he turned his fire on them. Conservatives would be chortling - and rightly so! Not because liberalism needs to purge or marginalize its Keith Olbermanns, or because impassioned liberal entertainers don't have a place in left-of-center discourse - but because when your political persuasion faces a leadership vacuum, you don't want to have it filled by someone who appeals to an impassioned but narrow range of voters, and whose central incentive is to maximize his own ratings.
Remember when National Review ran a cover story about Howard Dean, entitled "Please, Nominate This Man!"? That's how liberals feel about Rush Limbaugh at the moment: They can't get enough of him. I don't see any reason why conservatives should be playing into their hands.