I wonder how much shared accounts complicate recommendation engines like these. My wife and I both use the same account for netflix and for amazon purchases. I can't imagine that an outsider looking at our movies and purchases could make much sense of it.
What other people read/buy/like alone is near useless data. Garbage in, garbage out.<p>I can't believe people are still trying to wave their hands and pretend they have some amazing algorithm to turn this data into half useful recommendations.