Howto figure out whether two lists have any elements in common

While working with FragIt I had to figure out whether two lists had some elements in common (it does not matter which!) and I came up with the following piece of code (with the help of Google and Stack Overflow of course)

It takes advantage of the highly underused Sets available in python on which we can do some neat mathematically sane operations. I guess people just go for Lists and work their magic on that.