Hopefully I'm going to add to this discussion.
If sites at school, or work, were not banned, the workplace would have no control, education seems to be more strict, as you have minors that have access to the Internet, when if you're at work, the security of the sites is there, but less.
If you get what I mean, that's why sites like goatse, shock sites, generic crap, porn, need I go on? Is blocked :<
Going to spain again on the 17th to the 24th of August 2008 after I leave school, so probably won't be around as much during that one week period.