Do you really want to log in to all sites with your Facebook ID?
Nowadays, it's easier to stay anonymous in your local grocery store, than online. I kid you not. I have patronised my grocer since 5 years. I estimate that I spend upwards of Rs. 24,000 per year with him. I doubt if he knows my full name. If I did not ask for home delivery, he would not know my address. He does not save my mobile number and he has no way of hounding me if I never visit him again. These oases of anonymity are rare to find in modern times. As a user, have you noticed that on any news site or ecommerce site, you are being urged to sign in with Facebook, Twitter, Google or some other platform where you are an existing user? In the old days, every site would required us to sign up individually, and we did it cheerfully, because we really needed those sites. And let's face it, there were not so many sites. I recall maintaining a dog-eared notebook with a handwritten list of user IDs and passwords on different sites - Yahoo!, YouTube, ICQ, Rediff, GeoC