Now, I dislike Microsoft as much as the next Linux/Mac advocate, but I don't think their response to this employee makes them any worse than other companies in industry. Like the other guys were saying... you can't have an employee going around on a closed campus taking pictures... it's just not a good idea. And since this guy was just a temp, they would be foolish to feel any obligation to give him another chance.
The only reason I'm reiterating what others have pointed out is because I've seen many Mac users saying silly things on other message boards about this topic, but it really makes us look petty and ignorant. Microsoft has tons of Macs around for testing and graphic design purposes... I highly doubt that they're ashamed or trying to be secretive about this known fact. But when we go around saying, "Look, Microsoft uses Macs," and "Look, M$ sucks and they're mean to a Mac user because he uses Macs!" the whole community suffers. I hate seeing that.