Shortcomings of GA site overlay: http://www.lunametrics.com/blog/2009/03/17/site-overlay-issues-google-analytics/ It counts pageviews, not clicks on particular links, according to this blogger.
Alternatives: http://www.lunametrics.com/blog/2009/03/27/alternatives-site-overlay/ Some services offer detailed click analysis, but they’re not free.
Here’s a good list of automatically mined network visualizations, mostly leveraging Internet data. Found it while searching for do-it-yourself network visualization tools which I could use to play with my own real network relations and embed in my blog. We’re looking at ways to track link utilization on the virtual home website – the visualization show above from Crazy Egg is certainly a neat trick (if not actually analytically useful)