I'm always suspicious when I click "Sign in with X" and it prompts me to enter details. Normally I would already by logged in. But not always, for instance I mostly use Firefox on my phone, and those sessions aren't shared with webviews. So one can never know.<p>There's really nothing stopping anyone from making an entirely fake "Sign in with X" popup and people would believe it (me included), I think teaching people to give away their Google, FB, GH etc credentials on random pages is scary.