Moral: don't use users' contact lists to bootstrap or enhance social services. Barring strong differential privacy implementations, it will cause problems.
Implementing a 'what friends do I have on this service?' feature is one thing. Retaining that data and feeding it in to the recommender is very likely to cause this kind of problem.
Moral: don't use users' contact lists to bootstrap or enhance social services. Barring strong differential privacy implementations, it will cause problems.
Implementing a 'what friends do I have on this service?' feature is one thing. Retaining that data and feeding it in to the recommender is very likely to cause this kind of problem.