The next step is to find a community with an incentive to publish assertions. I agree that the big players (e.g. Amazons, EBays, etc.) won’t use the system. But imagine you are one of the numerous smaller auction sites trying to solicit sellers. Being able to publish reputation data in a way that the seller can use to build a reputation on other auction sites would be a competitive advantage that would cost the small auction site nothing. And when you are competing against EBay you need every advantage you can possibly get.

Similarly one can imagine price comparison websites also using reputation assertion publishing services since their goal is to give their users as much information as possible about the sellers and since each of them collects relatively little data banding together to share reputation data helps everyone. Again, this has no real cost to the comparison pricing websites and it benefits all of them since none of them yet has a very large reputation database.

I can only see blogs adopting a reputation system. I can identify other blogs I trust and say “if someone got a post accepted by any of the following blogs then let that person post on my blog”. You can also easily see services like Akismet also using reputation data to mark bad comments.

So I think there are a number of on-line communities that would be interested in adopting a portable reputation system but none of them is interested enough to do the work themselves. So the effort has to be kick started first.

The problem with adoption as you describe it is: what incentive is there for any single website to start publishing this data?

The data is definitely valuable to the group, as each benefits from the data published by others.
It’s a prisoner’s dilemma.

Tim O’Reilly argues that many web 2.0 businesses rely on “data inside”, using data as an advantage to lock the user in and attract more users. It seems counter-intuitive for such businesses (ebay, amazon, …) to release some of their control.