[amazon_not]

All that is all good and well, but for two things:

- it took me less time to input enough ratings to get useful recommendations than to register

- the registration asks for unnecessary information

Solution: if you don't want cruft in your dataset throw away recommendations not linked to a registration. If the users finds the recommendations useful, offer to save the profile by registering.

It's not like you are going to get any less cruft by forcing users tonregister. The only difference is that you are going to end up with a lot of throwaway accounts.