Some pretty astute observations in this piece. Basically, Greenwald pins it by saying Beck is the class clown who's always looking for attention:
Increasingly, there is great difficulty in understanding not only Beck's political orientation but, even more so, the movement that has sprung up around him. Within that confusion lies several important observations about our political culture, particularly the inability to process anything that does not fall comfortably into the conventional "left-right" dichotomy through which everything is understood. Some of this confusion is attributable to the fact that Beck himself doesn't really appear to have any actual, identifiable political beliefs; he just mutates into whatever is likely to draw the most attention for himself and whatever satisfies his emotional cravings of the moment.And a lot of that is simply a means of maintaining his cash flow. The point is this: If you're willing to say anything, why should we take you seriously? You're just the latest incarnation of Limbaugh, Hannity, Coulter, and all the other residents of the egg sac. You've got to keep escalating the rhetoric in order to keep the beast fed. And eventually, the movement to which you ostensibly align yourself is increasingly marginalized.