Well, when I got the device, the Lyft app was not installed. I visited the Play store, installed the Lyft app and ran it, and then: the Lyft app immediately signed me in, told me that my full name was Britney G-------, showed me "my" full e-mail address, and offered to let me book rides on her behalf, paying with her linked Visa card. It wasn't even clear how to switch accounts; it was like they were using the phone # as a primary key.

I sent Samsung some feedback about this but don't think the issue was on their side per se.