[heydenberk]

>> Before Google released Plus, the company might not have known that you were the same person when you searched, watched videos and used maps.

They did know that you were the same person. You maintained the same session. They may have had limited legal ability to actually use the data from the different services, but I imagine that could have been accomplished with a Terms of Service change without a new over-arching social application.

[okasaki]

That's exactly what they did. In Jan 2012:

http://googleblog.blogspot.com/2012/01/updating-our-privacy-...