Wouldn't it be cool if Amazon let you remove a book from its Book Recommendations? I really like the selections they recommend for me, problem is, they know my reading habits so well, they suggest things I've already read. So why can't I click someplace and say, "hey please don't show this to me, I've read it already"? That would improve my user experience and increase the likelihood I'd buy a book, which is what they're after in the first place.