Exactly. I think that Google could actually solve this single-signon problem by encouraging more website to auth with Google. They should stay clear on permissions tho and not ask me to connect the rest of the internet to my Google+ account, otherwise I would shy away from this solution much like I shy away from Facebook. Actually, right now I trust Twitter the most, when it comes to authorizing apps; not sure why that is though. Maybe because I am under impression that Twitter isn't going to post more cat pictures to my profile just because it can.