Freakonomics presents their annual baseball post with the suggestion that research underway there points to batter protection making a difference. However, make sure you read J.C. Bradbury's comment.

It's always seemed to me that protection should decrease the OBA of the batter protected, making it a counter productive strategy. Protection is supposed to prevent walks to a batter. But we know that if you take away walks, you reduce a player's OBA to his batting average, and for the great majority of players, that's a lower number.