While the obvious retort from the company would be "Why don't you do some work around here?" I do find that incredibly short-sighted. There's quite a few articles out which point out that a small amount of web surfing (10-15 minutes every couple of hours) is quite beneficial to both morale and productivity, not unlike the "cigarette break" of yesteryear (that's still allowed at many companies to this day).
If I were in charge of IT and worked for a company too paranoid to manage their employees properly, I'd try to find a system whereby an employee could "log on" to the general web (not porn or anything, but shopping or what have you) for 15-30 minutes a day so that people could "recharge" during the day.
Of course, if I was king of the company I'd just state that anyone who's performance wasn't up to par better not be spending all day surfing the web or they'll be on the curb sitting next to a box of their stuff...but ya know, the whole "management has a job to do too" angle never seems to go real far. If you can't trust an employee to do work, why are they an employee?
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"But there's no sense crying over every mistake,
You just keep on trying till you run out of cake"