I had a job once where they did that. We were a computer parts reseller, like to end user and small business customers, that sort of thing. They would just log on to our machines arbitrarily throughout the day and check out what we were looking at. It was their right and all, since it was their equipment, their policy, etc.
But anyway, I got tired of it one day and downloaded a bloated overkill of a anti-monitoring program from a guy's website and buried it deep down in my hard drive and installed it. He was just some bitter software engineer that a buddy of mine in the ATF had told me about. He wasn't a criminal or anything, he had just been laid off and had a ton of kickass freeware stuff on his website.
The day after I installed that thing there was a helpdesk tech in my cube "checking some things" when I got there. He fumbled around, checked the registry, and left. The next day a different guy showed, and he checked some additional things. That same afternoon a third guy came and replaced my CPU. He was like "We were having some issues with your hardware."
