I suppose you do it similarly to the way Amazon or iTunes implements it for reviews...you make sure the user is logged in via a Google account. Sure, it could

I suppose you do it similarly to the way Amazon or iTunes implements it for reviews...you make sure the user is logged in via a Google account. Sure, it could be exploited, and I'm guessing that's why they haven't implemented it, but there's got to be a solution that would make it work.