Google messed up when it tried to make some master account with Google+. Maybe everything could be incorporated into one account, but the way they've done it is one of the most complicated and confusing systems I've seen in computer engineering, and that's pretty sad considering it's Google.
Take YouTube. When I go there now, I have my Google+ account, but I have my old YouTube account that has been consumed by the Google+ account, but yet it's still separate on YouTube?? Now when I use YouTube, I have to make sure it's my old YouTube account being selected instead of my Google+ one. Why is this so hard? What's going to happen to my old YouTube account when it gets owned by this new "Google Account"?
If you can't do this right, which is obviously an issue, then just keep everything separate. Stop Google-fying services that are separate.