According to previous reports quoting documents that were taken by Edward Snowden, former NSA contractor, the two organisations have not only been mapping data of users, using realtime social traffic, and even smartphone apps, but have also been exchanging the same since 2007. The documents themselves date back to 2010.
The GCHQ is said to have been working under an initiative called Squeaky Dolphin ('sneaky' would have been more apt), wherein according to reports by NBC News, it was able to physically tap lines carrying global web traffic to extract key data about specific users. Reports also suggest that the GCHQ can keep track of YouTube traffic, links that are liked on Facebook, and the blogs visited. Eventually, the data collected in bits and pieces, when put together, gives a broader data trend in context with world events. It keeps government agencies updated on the trends and how they could possibly affect in the future.
But just like its friendly neighbour, the NSA, the GCHQ too has issued a statement claiming that the work they do, is carried within the purview of the law. The NSA, of course, had claimed that they were interested in foreigners, who were possible threats. The likes of Google, Facebook and YouTube have claimed that, if this had been done, then it was without their knowledge and that no one had given the government any prior permission to do so. Remember project MUSCULAR, the super-villain NASA and the victims Google and Yahoo. A sense of deja vu perhaps?