Ever been surprised by the "People who bought this also bought.." links on Amazon? Well some chap has written some code that tracks through these links to find a path between any two items. For example, you can connect people who bought Clocksin and Mellish's Programming in Prolog with people who bought Britney Spears' Baby One More Time in 14 hops. It's the fatal plunge into Celine Dion that does it.