Princeton did a recent study, where they predicted that Facebook might lose up to 80% of it's users in the period between 2015 to 2017.
Facebook responded as it was bitten by a rattlesnake. They now predict the downfall of princeton as a reponse.
A bit childish response in my opininion, but they claim they are using the same methods princeton used on their prediction. Impossible to verify, since they do not publish the data source, they used. Besides the statistics from facebook, they off course have and could be checked.
Anyway, very interesting document and prediction.