How about March 1999 - US Patent 7,962,367
"As shown in FIG. 4 the present invention may include, but does not have to include, a user preference monitoring program."
"The preferences may comprise a list of the type of products that the user has purchased and the frequency of those purchases."
"For example, a user that has a preference for company X's ...
This book was published in 2007: http://shop.oreilly.com/product/9780596529321.do Chapter 2 seems to cover much of this patent, specifically Collecting Preferences, finding similar uses, recommending items and matching products