Oh, okay: "slashdot karma" and "perlmonks xp" are roughly equivalent concepts. Points assigned to a poster by a community of readers.
Slashdot was one of the first places to experiment with such things, which is why the slashdot experience is somewhat relevant to this sort of discussion.
Oh, and it appears that "reputation server" is a slightly more obscure term than I thought it was... there's no wikipedia entry for it yet, for example (I'll have to put it on my list). The idea is something like the way ebay works:
you vote people you deal with up or down, and other people can use this to decide if they want to deal with them.
Note that in the ebay context, "reputation" is a serious business, it's not just points in a game.