For example, if you go to the "The Da Vinci Code" listing on Amazon.com and scroll down a bit, you will find this section:
Statistically Improbable Phrases: cilice belt, lame saint, seeded womb, lettered dials, corporal mortification, rosewood box, sacred feminine, royal bloodline, stone cylinder, sweater pocket
Amazon's says this about the feature:
Amazon.com's Statistically Improbable Phrases, or "SIPs", show you the interesting, distinctive, or unlikely phrases that occur in the text of books in Search Inside the Book. Our computers scan the text of all books in the Search Inside program. If they find a phrase that occurs a large number of times in a particular book relative to how many times it occurs across all Search Inside books, that phrase is a SIP in that book.
A bit of Google'ing in the blogosphere seems to indicate this feature appeared in mid-March. I actually stumbled across this on my own when looking at Amazon.com.
I wonder if this feature will interfere with people who like to googlewhack?