Perhaps if you don't realize you're logged into gmail. I thought it was well understood that being logged into gmail meant you were logged into all of google's services?
I am logged into 2 Gmail accounts at the moment, which one did it connect with?
You'll find out when you get an e-mail to one of the accounts.
It asks me to sign in when I click "Request Invite" in a browser that has never logged in to google. Also asks me to sign in if I've signed out of google.