Yesterday, I made the NSFW Pattern, a really simple design pattern and GRDDL profile for noting that a site is not safe for work.
It also serves as a demo of the potential simplicity of the upper-case Semantic Web, since if you follow the design, you are contributing to said upper-case Semantic Web. You can also 'fork' the profile by creating your own (please e-mail me if you wish to do this and I'll help). The CSS and JavaScript capability can remain because of the use of the class-name, but you can define more explicit meanings by creating your own profile. I could see, for instance, community sites like digg or MetaFilter creating their own profile, which they would define in certain ways. Fark has guidelines as to what they consider NSFW, and MetaFilter has - like is usual over there - a long discussion over exactly what NSFW means (where there is some rough consensus, even though it's subjective).
