Been in a few three way link exchanges in the past, both inadvertently and conspired, they seem to work good for a while, but then the without warning the link-love and authority is gone, along with some pagerank. I think Google is smarter than that, they can easilly detect a 3-way link; now social networking links magnify the order of probability and the difficulty of detection, I think that's the way to go; 100-way links, 1000-way links, 10,000-way links; get ya head around that Mr Brin.