Due to the large volume of Blazer fans complaining about how Yao gets away with contact on Brandon Roy's drives, I found this excerpt pertaining to fouls underneath the basket from a larger transcript about NBA officiating (interviewing the director of officials) that can be found here.
Here is the relevant paragraph about how defenders in the restricted area can avoid committing a foul:
"Even if he is in the Restricted Area, a Secondary Defender will not be called for a blocking foul if contact is made while he is alighting vertically in an attempt to block the shot, or if the drive starts inside the lower defensive box.
Offensive fouls can also be whistled, even if contact is made with a Secondary Defender inside the Restricted Area, if the offensive player leads with an unnatural knee or foot."
Analysis: Since Yao Ming is not chasing after Roy on the perimeter we can safely assume he is the secondary defender. Lets say Roy drives inside and jumps into Yao who is standing inside the circle, and Yao jumps with his arms straight up to contest the shot. BAM, contact and Roy hits the ground. According to the rules that is not a foul on Yao. If you think about it closely, if being in the circle was an automatic foul for big men trying to contest shots, centers would be fouling out by halftime. Now I'm not going to say Yao always goes straight up (I've seen occasions where his arms did bend down), but he does go up straight most of the time (unlike his first few seasons where he rarely did).
Hayes: The things I do for t-e-a-m...
Correct call: No foul.
Yao: Gudamn I'm gun feel dat in de morning.
Correct call: Offensive foul.
Joel: Oh crap! I fell too early!
Offensive foul. Just kidding, that's a flop.
Application: Worry not Blazer fans, this rule applies (rejoice!) to your team as well. As long as Oden learns to keep his arms straight up (the replay showed his arms were not straight up on the play where Brooks fouled him out), he will be called the same way Yao is. Well, I can't give you any guarantees as long as Adolf Crawford is an NBA official, but I hope this clarified some of the officiating misunderstandings we've all had.
Conclusion: Before Rockets and Blazer fans alike complain about Yao/Oden calls, watch closely if they go straight up or not before making judgement.