thesixtyone has a pretty good microreward system with their quests and user levels. I ended up micro-manging my next songs and listening longer on that site than I should have...
As much as I'm sure you're correct, I'm not sure my wife's discovery of said account would go over too well... It was for research into online reward systems, I swear!
-Yelp "Elite Users" get the little title next to their name if they post enough useful reviews. Likewise Amazon has their whole 'Top Reviewer' thing.
-Messageboards where members can give each other validation points, and then the amount of "rep points" someone has is displayed next to their name.
-Foursquare has the reward of making a user the "Mayor" if they post enough reviews about a certain area, and gives users 'badges' for completing different tasks. (I've never actually used it, but its something to that effect.)
Well you could list your karma along with their associated comments, someone might want to buy your output!
-edit: also, karma here isn't transferable, that's the problem, but people would like to have increased karma for status value, but that status value would disappear if it became transferable.
I almost feel like http://www.thewhuffiebank.com is also a good example of an attempt at microreward and reputation system on a grander scale.