Whuffie "Many community-oriented websites are experimenting with Whuffie-like concepts of reputation management (Slashdot's karma system, for example, or eBay's feedback ratings). Others look further ahead, at the "next generation" of the web - known as the Semantic Web.
One of the key challenges in developing the Semantic Web is in fact Whuffie, although you won't hear it called by that name.
Built of assertations about facts, the Semantic Web is basically distributed metadata. If one party says "Water is Wet" while another claims "Water isn't Wet", problems are encountered. At this point, Whuffie plays a role: which party is trusted more by others whom I already trust?
One of the key researchers in this area is Jennifer Golbeck, who is performing research on Trust in the Semantic Web"
This seems to imply that the Semantic Web offers non-monotonic, defeasible inference. Maybe it's just not a very clear example. A good run down is Non-Monotonic Logic (Nixon and Tweety are given examples, but not Clyde).