http://www.gamersdailynews.com/story-19369-ML...-Play.html

The big issue with extra buttons is how easy it is to mod the controller without us being able to monitor it. Modders will be able to turn the extra buttons into rapid fire buttons or a macro like RRX. We cannot simply check every player’s Onza controller to make sure they have not modded it. Sure, someone could do that now with a Microsoft controller, but by doing that they are removing a default button on their controller. People pay a lot of money now for modded controllers with extra buttons that will rapid fire or macro. The Onza would make it impossible for us to monitor this on the circuit.

just think about it: "dreamhack bans (your favorite mouse) from the quake tournament. has anything like that ever happened in the PC world? not that i know of.