In the wake of the disclosure that there were some shady things happening at HP while they were trying to find out who was leaking information to the press there is an article at http://redmondmag.com/features/article.asp?editorialsid=639 that talks about others who were doing things that were less than ethical. I remember taking a college class on ethics where we talked about issues such as finding out privileged information and what you should do.
I have been fortunate in that I have not had to be directly involved with any cases of spying or illegal activity at work. The closest I got was when I was the "webmaster" for a company and we were monitoring the logs on our proxy server. We had published a policy letting everyone know that they were being monitored but we still had an employee who decided to download pornography. I went in to the boss with the log files and left it up to them. The employee wasn't fired and I didn't see anything else going on that violated the company policy so I feel like it was handled correctly but like I said I was fortunate to not have to get in the middle of it.
It is a shame when people who have a good job that pays better than most feel they have to spy or cheat. I suppose we could blame it on a lot of things but it comes down to personal integrity and doing what you know is right.