There's an interesting analogy between Google Search+ and Microsoft Internet Explorer in the mid-1990s; let's hope it turns out better for Google.
In the early 1990s Microsoft didn't understand the Internet. Windows didn't even support TCP/IP, you had to download third party drivers like Trumpet Winsock to go online. And there was certainly no web browser, Netscape was going to sell that to users. Then in 1994–1995 Bill Gates executed an admirable turnaround at Microsoft with help from folks like Sinofsky and Allard. They quickly built a TCP/IP stack and a web browser and bundled it with Windows 95 and NT. Gates' memo The Internet Tidal Wave was the visionary document that explained it all. That rapid embracing of the Internet saved Microsoft as a company; they would have been doomed otherwise.
In the late 2000s Google didn't understand social media. They had some clumsy efforts like Orkut and Buzz but you had to go to MySpace, Facebook, Twitter, LinkedIn, or RenRen to get social. Then in 2011 Larry Page executed an admirable turnaround at Google, with help from folks like Gundotra and Horowitz. They quickly built Google+ and bundled it with the primary search engine. There's no visionary memo about Google+ in public but you can bet they have a very clear and strong strategy internally. The rapid embracing of social media is unprecedented for Google; it's commendable.
Microsoft's Internet strategy ended rather poorly for them. Their illegal, monopolistic actions finally met with an anti-trust investigation. The resulting settlement significantly weakened Microsoft's monopoly control and allowed room for companies like Apple and Google to flourish. Microsoft's still doing OK, but no one thinks of them as a major Internet innovator. (Despite having the only competitor for Google search in the US and Europe.)
Will Google's social media strategy result in similar anti-trust fallout? I don't have the legal expertise to say. So far all the anti-trust action has been around ads, but that's expanding. Google seems to be leveraging their market dominance of search and ads to compete in social media. Hopefully Google's smart enough to not be saying things about cutting off Facebook's air supply. But they seem to have made the bold decision to set aside anti-trust concerns and just go for it. We'll see if that works for them, I just hope they act ethically and leave room for fair competition.
Disclosure: I used to work at Google but left there over five years ago. I have an interest in Twitter, a social media company.