Google announced earlier this month its plans to shutter Google+, its failed social network, after a second security breach exposed the data of millions. Along with the social network, Google plans to shut down the Google+ APIs on March 7, 2019. However, some APIs may stop working even sooner.
There isn't just one social graph, there are many. LinkedIn maintains your professional contacts, while Facebook has friends and family (and yes, often many professional). Twitter has some mix, as well, perhaps with a different filter. Aggregators take these disparate contacts and bring them into one place. A new service uses several APIs to merge them and give tools to better understand and utilize your network of contacts.