I voted yes. I don't work right now, but the last place I worked had one. It wasn't enforced at all, but it was there. The network guy was too busy to even have a chance to enforce it, and besides, he broke more of the rules than the rest of us combined. We still had to be careful, though, because it could be used as grounds for dismissal, and the CEO was a very moody lady. You could be on her bad side without even knowing it, so you wouldn't want her to catch you.