@Matt : "sleep for zero milliseconds" and "do nothing" are emphatically *not* the same thing, semantically or otherwise.
Calling Sleep(0) let's Windows *know* that you have nothing to do, and that you are so intent on doing nothing that you are happy to give up any remaining part of your time-slice if Windows so decides.
Doing nothing and letting your manager KNOW you are doing nothing (Sleep(0)), is very, very different from just *doing* nothing (FaceBook()). :)