Good Works, Bad Works, but Karma doesn't work

Stowe Boyd shines a warm, bright light on one of his blogs regarding what he sees as a key need that's been so far unfulfilled during the emergence of Web 2.0 applications. Stowe mentions Oyogi in an illustrative example regarding the reputation of users. Take-aways from Stowe's post are: (1) that in this era of the 'mashup', it would make sense for the concept of social karma (e.g. reputation) to be transportable and understandable across a variety of sites - an open exchange between various applications and services (2) this naturally leads to the concept of aggregate (universal) karma. He  makes an excellent point and it is a worthy concept to seriously consider. As with any good idea, there are challenges of course. Do you weight karma differently based on the maturity of the site? The longevity of the user? The activity of the user? Should their be a central "clearinghouse" of sorts? Do you display an aggregate reputation rank? Sub-rankings for various sites? Do the way some sites compute Karma undervalue a Yogi's contribution,  overvalue it (see Richard MacManus' ruminations on this on ZDNet)? If so, is this fair to use in an aggregate ranking? Nevertheless -- all challenges aside -- its worth serious exploration ... Its probably fair to say that -- as long as you can interrogate a site's "API" to determine a user's Karma, and have and understanding of what that value means on the site's respective scale -- there are plenty of us out their who'll find a way to make it work. As I'm finishing this post, I read that MIchael Arrington profiled a company that was trying to take the lead in this regard back in August. He has a good thumbnail of iKarma there and some interesting comments from readers as well ...