Well at first glance I assumed that it couldn't be run correctly because of the dependency on "big.txt". But digging a little deeper it turns out you can download that file (which happens to be the Project Gutenburg text of The Adventures of Sherlock Holmes) from Norvig's website [1], so I suppose it is useful after all. But not exactly user-friendly.

[1] http://norvig.com/ipython/big.txt

Yeah, I can also execute it by myself but that's not the point.