Possible problems when changing TCCR2B ?

Hello,
I want to change the frequency on pin 3 and 11 to control motors (with the arduino motor shield r3).
These pins use timer 2.
My question: is anything else using timer 2 which may affect some other things ?

Ps: i got my information on this page:
http://arduino.cc/playground/Main/TimerPWMCheatsheet

tone and various libraries. In my experience, library writers are good at documenting what hardware they use.