Billions of users or not, becoming boring is a huge problem for Facebook. With a revenue model so heavily dependent on pageviews, they need to keep their users

Billions of users or not, becoming boring is a huge problem for Facebook. With a revenue model so heavily dependent on pageviews, they need to keep their users engaged and on the site... and that doesn't appear to be the case over the long term. New users ride a wave of heavy usage, but over time, Facebook takes on more of a role as a utility than a diversion. It has for me and most everyone else I know who started using it when it was a shiny new toy exclusively for college students. Facebook can't keep up the rate of new user acquisition it has enjoyed for the past couple of years forever - and as the userbase collectively ages, interest wanes, pageviews decline, and revenue drops off. Right now, it looks like they will inevitably be caught in the same race to the bottom, doing whatever they can to scrounge up page views, that Yahoo is in.