As gaika mentioned, the mechanics of this are pretty easy if you want to do a simple pagerank equivalent. There are a few caveats though: pagerank is a positiv

As gaika mentioned, the mechanics of this are pretty easy if you want to do a simple pagerank equivalent. There are a few caveats though: pagerank is a positive weighting only so you would need to google up "yaprank" (which I believe is the system jaanix uses) to see an example of how to deal with downvotes, you need to deal with rank sinks and other ephemera of the pagerank system, and you need a network that is large enough to let the ranking system bring real benefits. As someone who is working on a system like this that can also do realtime rank adjustments I can assure you that the mechanics are simple, the hidden details are subtle, and until you have a community that is active enough for this to make a difference it is hard to say that the effort is worthwhile.