Originally Posted by MR.nismo

I guess he is running a humongous turbo and in order to keep it "spooled up" he needs to rev that high. And yes, deeeeeep pockets are needed since at those levels of rpm's there is something giving way all the time.
I remember the Mazda RX-7 when people where pushing the 9,500 rpm band and flywheels were coming of the vehicle thus injuring the drivers. But it can happen in any engine that spins that fast.