Watching Wishlists

Data Mining 101: Finding Subversives with Amazon Wishlists:

Amazon wishlists lets anyone bookmark books for later purchase. By default these lists are public and available to anybody who searches by name. If the wishlist creator specifies a shipping address, someone else can even purchase the book on Amazon and have it shipped directly as a gift. The wishlist creator's city and state are made public on the wishlist, but the street address remains private. Amazon's popularity has created a vast database of wishlists. No index of all wishlists is available, but it remains possible to view all wishlists by people of a particular first name. A recent search for people named Mark returned 124,887 publicly viewable wishlists.For an all inclusive search by name, you could compile a comprehensive list of first names and nicknames from the baby names databases available on the internet. Armed with this list, and by recording the search results for each first name, it is possible for you to retrieve the vast majority of public wishlists on Amazon.

He then gives is a shot: "using a pair of 5-year-old computers, two home DSL connections, 42 hours of computer time, and 5 man hours, I now had documents describing the reading preferences of 260,000 U.S. citizens." Plenty of details if you want to try it yourself.