Facebook will lose 80% of users by 2017, predicted Princeton researchers in 2014

“Ideas, like diseases, have been shown to spread infectiously between people before eventually dying out, and have been successfully described with epidemiological models,” the authors claim in a paper entitled Epidemiological modelling of online social network dynamics.
“Ideas are spread through communicative contact between different people who share ideas with each other. Idea manifesters ultimately lose interest with the idea and no longer manifest the idea, which can be thought of as the gain of ‘immunity’ to the idea.”