Netflix Prize 3: How to create a meaningful database that is impossible to de-anonymize.
Likely, Netflix has the power to start it's own social network platform based on it's existing users' movie preferences. Some user's might be proud to say that they rate specific movies highly, and correlate to particular algorithms based on collective opinions.
For instance: 'Click here to add user X's preferences to your algorithm for Y genre'
See this: http://godplaysdice.blogspot.com/2009/12/uniquely-identifyin...
I imagine gender and DoB factor in heavily to something like a recommendation engine, and I'm sure zip code would come into play when trying to get those last couple percent as is the case with the Netflix prizes.