We tried to outline some of the challenges of building such a system in our NANOG52 presentation:
http://www.merit.edu/networkresearch/papers/pdf/2011/NANOG52_reputation-nano...
In particular see slide 4. where we tried to lay down what we think the requirements are for a socially acceptable reputation system.
With a bit of luck we might be able to announce the release of our system before the next NANOG mtg, but in my opinion collating host reputation reports is just a small and the easiest part of the effort. The key is in solving the challenges of allowing (and incentivizing) participation and being robust to false information injection.
I've actually encountered a system that was accepted for operational use once. Bad data was added at some point (bound to happen) and the system was shut down. Thanks for sharing your slides, keep up the good work! Gadi.