At least a half dozen times I have clicked on a public google+ post only to be coerced into attaching my google account with a google+ account. Screw being able to read said PUBLIC posts. My solution has been to logout and read it. But I'm sure plenty of people fill up that form mostly out of disdain and google gets to count them as a new user.
Really, getting new users by uber trickery is bad not just for the user but as much for Google Inc because it isn't a signal for a quality product(in this case, the exact opposite).