Less Wrong seems like the ideal community to think up better reputation systems. Doctorow's Whuffie is reasonably well-thought-out, but intended for a post-scarcity economy; but its ideas of distinguishing right-handed (people who agree with you) from left-handed (from people who generally don't agree with you) reputations seems like one useful ingredient. Reducing the influence of those who tend to vote together seems like another potential win.

I like to imagine a face-based system; snap an image from a smartphone, and access reputation.

I hope to see more discussion, in particular, VAuroch's suggestion.