The other day Devlin Daley pointed out RightCart to me. RightCart is a SaaS shopping cart implemented in Rails. The reason RightCart caught our attention, besides the fact that it's pretty slick, is that it uses RapLeaf's rating system as a way to rate merchants.
Coincidentally, the next day, Scott Allen pointed to some survey results he had about Rapleaf and "transactional trust." The survey showed that ratings are the number one way that buyers choose merchants.
Ratings are one way that people establish a reputation for a merchant (or a buyer when two-way trust is necessary). One of the problems with ratings is that they're not usually transferable from site to site. For products that's not such a big deal. I can read customer feedback and look at ratings for a Nikon lens on a number of sites and feel fairly confident that they're talking about the same things.
ClaimID is one way people can start to aggregate information about them. In a post on the ClaimID blog, they talk about the Allen survey and how ClaimID could help. The problem with that is that it's strictly voluntary. Nothing makes me "claim" bad ratings.
I think that Internet-wide, cross-site reputation systems need what RapLeaf has, what ClaimID has, along with some other features as well, including the ability to automatically query Web-based sources of data. The reputation system we're building is meant to be a testbed for exploring these ideas.