I recently received a digital box from my cable company and I just love the PIN number feature. My son likes to sneak around and watch shows like South Park and other various things his brother is old enough to watch so I graciously added a PIN number to anything PG-13 and over. He wasn't very happy.
He recently went on restriction to the point where he can't even watch television but for a 1/2 hour a day if he does his home right when he gets home from school. I conveniently locked the PIN code for ALL channels :) Now he can't even watch Sesame Street if he wanted to.