Researchers at Princeton University used a Susceptible Infected Recovered model to predict Facebook use to decline like a disease dying out.
Social networking sites have been found to go through the same phases as infectious disease. Ideas, like diseases, spread rapidly, grow old, and die out.
Like many sicknesses, social networking is spread by contact with friends. Because of this, sites like Facebook initially experience exponential growth in users. Eventually, the growth slows as users lose excitement. Researchers John Cannarella and Joshua Spechler compare this to the development of immunity to a disease.
The last phase of the model is abandonment. Facebook is already in the early stages of decline. MySpace, a similar social networking site, experienced a decline even steeper than its growth, peaking in 2008 and becoming obsolete by 2011. Cannarella and Spechler predict Facebook nearing this stage of rapid decline.
Facebook says that it has already seen a decrease in teenage users as other sites become more popular.