Well that's because Yao has a lot of games where he gets neutralized by mediocre/average centers like Troy Murphy, Kendrick Perkins, Memet Okur, Samuel Dalampert, fronting defenses, altheletic/physical powerful forwards, etc, etc. I've never seen a star player get taken out of the game so easily as often as Yao. He also doesn't rebound well either.
I think some people over rate their knowledge of BB, when they don't realize how much players like Yao do even without the ball. TEAMS GAME PLAN AGAINST HIM EVERY NIGHT He may not get the respect he deserves ever on this BBS, but the rest of the league knows better and I trust them before myself or any one else on this site.