Blocking the "popular" sites will only stimulate a lot of creativity in finding workarounds or other sources of the material. Which do you want - someone who visits a few sites on a regular basis or someone who visits A LOT of different and NEW sites to find what you're trying to block him from finding? To me, at least, it would seem that the risk of infection is proportional to the number of new sites visited...


Either take the bullet by the horns (actually talking to this person...) or find a way to lower the risk (securing the browser, system etc). Porn is not the only source of malware/spyware/grayware/adware/whatever-ware, so any steps towards increased security is well advised anyhow.