There's been a bit of discussion on the newsgroup uk.gov.local on the issue of whether public servants should have general web access from their work computers. That prompted the following from David Sim (quoted with his permission):
"We do debar pornographic sites, particularly where people are likely to stumble across them (as was possible with alta-vista for a while). However, debarring on the basis of keywords can be difficult - we tried it and had problems accessing Sussex council and the Scunthorpe web sites."