Thanks to Plus, Google knows about people’s friendships on Gmail, the places they go on maps and how they spend their time on the more than two million websites in Google’s ad network. And it is gathering this information even though relatively few people use Plus as their social network. Plus has 29 million unique monthly users on its website and 41 million on smartphones, with some users overlapping, compared with Facebook’s 128 million users on its website and 108 million on phones, according to Nielsen.
The company has also pushed brands to join Plus, offering a powerful incentive in exchange — prime placement on the right-hand side of search results, with photos and promotional posts.
As always, all data collection done “to create better products” (i.e. more relevant ads).