We (LearnBoost) were the ones that put it up about a year ago after about an hour of work - it's a simple but powerful concept, in theory [1].

We ended up taking it down a month or two ago because it never really grew into anything significant.

Hopefully this new version works out better!

[1] Post about our version: http://blog.learnboost.com/blog/hackernews-for-education/