From memory there was a few, but I've lost the links file I had. Contenture was one of them. There was a project at one of the journalism schools trying to push the same model too.

It's a good idea on paper, but actually making the market-building side work is really hard.

I've been focused on the technology side because hey, that's how I'm wired. Essentially, you can't rely on standard web bugs or javascript approaches; they're much too easy to subvert.

In my honours dissertation I identified 9 distinct attacks on the "naive" protocol and developed countermeasures for each. But that design is fatally flawed too. I have another design which ... well, watch this space: http://robojar.com/