it was always a big question in front of any product person. It was primarily relized by user's own behaviour, people started using so many sites, it became alm

it was always a big question in front of any product person. It was primarily relized by user's own behaviour, people started using so many sites, it became almost impossible to keep a seperate user name for so many logins. In case they tried having a usique namer over a new property, sometimes it was avilable sometimes it wasn't. Hence, email based login became omnipresent Social logins / Open authentication were also tried. They are at many places, but they also pose some challenges. There isn't a simple answer yet, but may be in the future, a device based finger printing, eye scanning or something else may be the answer For now, or some years back actually, I gave up and chose Email based authentication.