A platform for this has existed almost as long as the web itself. PICS is a W3C standard for labeling content. There is a working draft out for an RDF-based version of PICS called POWDER.
PICS ratings are assigned by the IRCA, now part of The Family Online Safety Institute.
The problems with PICS adoption were predictable. First, like with the V-Chip, few parents enabled content filtering on their browsers, or even knew that feature was available. Second, the honest content providers, the ones who got their sites labeled for language, violence, or adult situations, got screwed because of all the sites out there who didn't opt into the system, and which could be viewed by everyone.
This looks like an interesting marriage of the web and the desktop. In Pyro, Web apps run in windows on the desktop, right alongside desktop apps (through compositing). Features expected in a desktop environment, like task/window selection and an Expose-like function, are written in Javascript."Pyro is a new kind of desktop environment for Linux built on Mozilla Firefox. Its goal is to enable true integration between the Web and modern desktop computing.
Real Programs don't use shared text. Otherwise, how can they use functions for scratch space after they are finished calling them?