Many employees worry about WebSense and other logging apps but in my experience, those apps aren't what gets you in to trouble. I've never seen an investigation start with the logs...but I have seen a couple of senior execs fall after the board started an inquiry in to some internal financial issues and the investigators found porn on the execs computers. As soon as they find out they go pull the web logs and then things spiral. So often these logs aren't really the target of the investigators, but if they're looking for something else they sure can hang you. Like I said, I've seen a few people get taken down for things like this when the actual investigation found they did nothing wrong.
So be careful. Don't be an idiot. Don't be the CEO looking at porn at work when you can do it at home. It just doesn't make sense. What's sad is I'm sure some of these guys look at porn at work because their wife gets mad at home. Nice job honey. :)