Wired's Ryan Tate makes the case that Google Plus should be treated not as Facebook's challenger but rather as background infrastructure. ("Plumbing" is the word used.)
[R]elatively few people use Google+ for active Facebook-style “social networking.” But it provides a way for Google to track your behavior and data across all its other services. That makes it useful to Google and useful to people who use Google. It will never be Facebook, but it doesn’t need to be. In the future, even Facebook doesn’t need to be Facebook.
As Facebook has discovered, a sprawling, strongly-branded social network isn’t as relevant in the new world of mobile devices, where people want narrowly-targeted apps. But the underlying fabric of a social network can provide a common back-end for those apps, making them easier to configure and monetize. That’s why Facebook has been ripping functionality out of its big broad main app and shifting it to its more specialized apps, all united by the company’s social plumbing.
Over the past two and a half years, Google has been laying much the same kind of pipe, putting Google+ plumbing behind apps like Hangouts, YouTube, and Snapseed. This means that, in addition to serving as a forum for Facebook-style status messages, Google+ has always played a simultaneous role as a social layer that powers Google as a whole, letting the company centralize information about your likes, interests, and background that it can use to target premium advertisements. That is its main strength.
Google may or may not continue to push Google+ as its own “product,” but whatever it does with the front-end of Google+ — the website and app people actually interact with — it won’t be that important. For one thing, people already have Facebook, and the Google+ front-end doesn’t give them much that’s different. “G+ didn’t work as an actively-used social network because it provided no new features users wanted,” says Clay Shirky, an NYU professor who has long made a study of online groups. “The networks that have done well post-2010 are those that provide new kinds of messaging, not new kinds of linking: Instagram, Snapchat, WhatsApp, WeChat.”