I particularly like this excerpt on whether recommendations should target what you think you want or what you really want:
The goal of Amazon's recommendations is simply to generate more sales than whatever would have been at the top of a customer's page without personalized information.Implicit data like purchases may be noisy, but it also can be more accurate. You may say you want to watch academy award winners, but you really want to watch South Park. You may say you want to read Hemingway, but you really want to read User Friendly.
It's bizarre to expect Amazon to ignore the trainloads of "Star Wars" stuff I've bought from it, or to somehow detect that I thought all those Boynton books were insipid even as I kept buying them. When it comes to describing us as customers and consumers, recommendation engines may do the job better than we would.
In other words, we lie -- and never more effectively than when we're lying to ourselves ... I fancy myself a reader of contemporary literature and history books, but I mostly buy "Star Wars" novels and "Curious George" books for my kid.
The best guide to what you will want is what you wanted.