This is solving the wrong problem. What I really want is a service that tells me if a particular link is NSFW. How about a Firefox plugin which links back to a database of NSFW links on a server somewhere. Then, whenever I click on a NSFW link on Reddit, a little box can pop up saying "warning, don't view this at work" and I have the choice to wait till I go home to visit it.

Seriously, it's a great idea and I would totally implement it if I had the time/motivation.