I have similar problems with Amazon's "you might also be interested in" functionality. Neither Amazon nor eBay really seem to have the slightest clue why I might purchase any particular item, how that might relate to other items I've purchased previously, or how to use that to extrapolate other items I might actually be interested in. I have had Amazon recommend to me books that I had an interest in... but those were often ones that I had previously purchased... from Amazon!
I'm fully aware that an algorithm to predict the buying habits of any given customer is an insanely difficult thing to program, and I laud so many folks for even attempting it. But for as much credit as these folks are given in business circles for coming up with such great ideas, I have never found them to be remotely useful or effective. Am I alone in this?