OFFICE ETIQUETTE:
Here's one of the worst traits in a human being ever: personal guilt breeding paranoia. We've all felt it, and sometimes succumbed. But what's inexcusable is watching over your coworkers. If someone wants to chill out and enjoy some "me" time at work, and it doesn't make more work for you, who cares? Even if it does, let's learn to cooperate and take turns slacking. This isn't kindergarden; we're adults, we can do this. Watching out for the other guy ruins everything, so let's drop the big brother act and get back to the more important business of looking out for communists (don't forget - they could be anywhere!).
It's just polite...