April 7, 2010 update
What I also saw is that the Extension:UsabilityInitiative, that is active at Wikipedia, uses Click Tracking as part of the Beta rollout.
What I like is the programming language R which is able to W:Cluster analysis. We have got a Wikibook Wikibooks:Data Mining Algorithms In R. But clustering works with numbers, not with click paths. I wonder if it is possible to transform click paths into numbers.