@hideki Really this is just an attempt from google to get people's numbers to further track them. In security two factor means needing two different means to access something, so a password (something you know) and a phone (something you have) is good in theory until you realize it's actually one factor because the phone is a recovery option for a password. And it's even worse than passwords because if someone can reset all your passwords with one vector you might as well just use the same password for everything since linking a number literally grants you a single point of failure. And said failure is some outsourced indian guy who's getting paid pennies on the hour who hardly understands english who can easily be tricked with basic social engineering
*is going to