The certification scheme here is interesting. I'd like to see a more general purpose scheme, and more information available for certifiers.
The Slashdot scheme assigns karma based on more frequent feedback associated with commentary. It is thus nicely tied in with behavior in the community (writing good comments). It also makes more use of the assessments (by allowing users to filter content by how highly rated it is). Advogato is getting to the point where scaling issues (number of comments on each article) are important, and a moderation scheme that is somehow tied in with the certification scheme would be useful in a lot of contexts besides the mission of Advogato.