The game asks for a lot of information from your Google account. If you use your iPhone or Android and log into the game with your Google account you end up giving the game full, unbridled access to your account. Is this safe? Um no.
I still remember those FBI warnings on VHS tapes? screaming at you in bold lettering that you'd be smacked $250,000 fine if you put tape over the square on the spine and copied it? Here's the digital age version of that FBI WARNING!