Baseball Prospectus has a good article on ESPN regarding the MVP-caliber season Jeff Kent is having and the lack of respect he has gotten in the MVP debate.
Bill James, I believe, wrote something about this in Win Shares when he compared his Win Share MVPs against the real ones. He noticed that a player could have almost as good or an even slightly better season than his MVP one and get completely ignored. James thought it had something to do with expectation levels already having been set for the player. Unless the player far exceeds this level (e.g., Bonds last year), he fails to get the recognition he deserves. I guess that falls under the rubric of human nature. Damn humans.