I think this move comes down to issues of branding with google accounts. What's happened here is replacing needing a 'Youtube' account with a 'Google' account,

I think this move comes down to issues of branding with google accounts. What's happened here is replacing needing a 'Youtube' account with a 'Google' account, which for all intents and purposes has been a Google account for a while now anyway. I have a feeling that this is the beginning of consolidating the various ways in which you hold a google account for any of the services under one G+ bannner. The problem I see they might have with this is issues of association on non-social networked activity with the G+ social network. I've found amongst my non-tech friends a strong opposition to moving from Facebook to G+ as they perceive Google to be less trustworthy than Facebook when it comes to matters of privacy, and in extreme cases to think that Google is actively evil in its data sucking in comparison.