As I mentioned earlier, we don't require a lot of private personal information in order to use the service. A lot of our recommendations are based on who you are already publicly following, for example. Perhaps the people you're already publicly following are also publicly following...for example, if you happen to follow a lot of the same people someone else follows, we may suggest you follow some of the people they're following but you aren't already following, because we assume you are interested in the same—
On December 6th, 2012. See this statement in context.