Facebook’s interest graph: People have usually described Facebook’s data trove as consisting of a “social graph,” a portrait of each person’s relationships. But since so much content is shared on Facebook — two posts daily per user, on average — it is more useful to think of Facebook as an interest graph, a window into what people care about. Facebook’s “like” button is pressed 2.7 billion times every day across the web.
The Google+ knowledge graph: Google+ is best thought of as a complement to Google search, and as a window into what people know or want to know. Google+ will help Google contextualize its trove of search data, offering hints into why people might be searching for certain kinds of information. The relationship goes in the other direction, too — the number of “+1s” and other Google+ data are now a top factor in determining how a Web page ranks in Google search results.