are two of the most popular social networks, both with respect to research efforts and user base. They have distinct broadcasting functionalities - microblogging and check-ins. While Twitter can reveal a lot about user interests, Foursquare check-ins provide a proxy for human mobility. In Foursquare users check-in to venues that they visit through their location enabled devices, and share their visit or opinion of a place with their friends. Foursquare is two years younger than Twitter and its broadcasting functionality is exclusively for mobile users (50M to date[^1]), while 80% of Twitter’s 284M users are active on mobile[^2]. Twitter generally allows anyone to “follow" and be “followed", where followers and followed do not necessarily know one another. On the other hand, Foursquare supports undirected links, referred to as “friendship". A similar undirected relationship can be constructed from Twitter, where a link can be considered between two users if they both follow each other reciprocally [@Kwak2010]. Since we are interested in ultimately in predicting friendship, we consider only reciprocal Twitter links throughout this work.

![Social network graph for San Francisco. Blue edges are single-layer edges, while pink edges are multiplex edges. The node size is proportional to the global degree of 