False Negatives (Score 1)

They don't work, anyway. As a sysadmin I ocasionally check the logs for the filtering software (Of course, I go around it, don't tell my employer ;) Every time I've seen someone try to find a porn site- he finds it. Sure, he gets any amount of blocked sites but, eventually, he gets one or two non-blocked ones. Also we continually have to adjust the policies to get around the false positives...