The anonymous login allows users to become less anonymous by providing real info if they wish to do so later. So you have the potential to get > 0 data. This w

The anonymous login allows users to become less anonymous by providing real info if they wish to do so later. So you have the potential to get > 0 data. This would basically make it easier to access or try out all the FB-only-login apps without giving the app owner all the personal info.