Excerpt from some interesting Google speculation
My colleague Eric had a very interesting theory earlier. Maybe Google’s real motive is to get the government to also look into Facebook’s often-unfair practices with regard to their network ahead of their IPO. If social and not search is indeed the future, call this pre-subversion. And if there’s any shred of truth to this theory, more power to Google — it’s rather genius (though still extremely risky).
But the more likely answer as to why Google is doing Search+ is much simpler. At a high level, they believe social elements are going to be an extremely important part of search going forward. Given that the two biggest players in social, Facebook and Twitter, don’t give them full access to their data (Twitter used to but the relationship ended, Facebook never did), Google is doing the only thing they can in their minds to still get the data they need: bolster Google+.