Consider the Netflix and AOL search data, where people <i>could</i> (maybe) be identfied from "anonymized" data.  Or the facebook gaydar thing.<p><a href="http://33bits.org/2008/09/30/law-review-article-about-netflix-paper/" rel="nofollow">http://33bits.org/2008/09/30/law-review-article-about-netfli...</a><p>harvesting emails, that is an established business model called...