From the Associated Press:
"Amazon.com Inc. has one potentially big advantage over its rival online retailers: It knows things about you that you may not know yourself.
"Though plenty of companies have detailed systems for tracking customer habits, critics and boosters alike say Amazon is the trailblazer, having collected information longer and used it more proactively. It even received a patent recently on technology aimed at tracking information about the people for whom its customers buy gifts."
Read more here.