I think the ubiquity of smartphones is a signifigant factor in facebook's decreasing engagement. SMS used to be useful mostly for coordinating once you were at

I think the ubiquity of smartphones is a signifigant factor in facebook's decreasing engagement. SMS used to be useful mostly for coordinating once you were at a location/event, or for reminders. Now that you can send links to arbitrary content, it replaces in large part what most people used facebook for, with much faster response times for the most part.