It's not necessarily on the main page for everyone though. If you go to someone's house who buys a lot of power tools, the front page may have drill bits, tool chests and jigsaws on the front page. You may have looked at something on Amazon that is related to Michael Jackson in some fashion (the Thriller 25 album, a Janet CD, a Jermaine CD, a Justin Timberlake album... who knows) and when you go back to the main page it shows you related items.
Try clearing your cookies and going back to the main page, then see what's on there.