Having just read the recent article in Wired, I'm curious: what is it about the Netflix Prize that's so challenging? I mean this in the sincerest way possible, I'm just curious about the difficulties posed by the contest. Are most recommendation engines in general this hard to improve? If so, why is that? Or, is Netflix unusually difficult to improve, and if this is the case, what's special about Netflix that makes this so much more challenging than, say, Amazon?
Because NetFlix already has a really good recommendation engine. If they knew how to easily improve it, they would have done so by now. Their whole business model is around cross selling products (movies) to consumers. The recomendation algorithm is really the core of their business. The better it works, the more money they stand to make.