There are voting systems which attempt to detect cliques or rigged voting. These are called "sybil attacks." There is a good deal of academic literature that

There are voting systems which attempt to detect cliques or rigged voting. These are called "sybil attacks." There is a good deal of academic literature that you can find on the subject, and attempts to reduce the weight of en masse voting by tying it to a probability distribution. I wrote a diary on this subject with some links if you're interested: http://www.kuro5hin.org/story/2009/12/8/01628/8328 http://www.kuro5hin.org/story/2009/12/8/01628/8328