Facebook's Mark Zuckerberg will eventually have to deal with the fact that all growth has limits.
Facebook's impending problem is that even if the company enables future pacemakers to share our every heartbeat, the company cannot automate caring—the most important part of the feedback loop that has driven the social Web's ascent. Nothing can support exponential growth for long. No matter how cleverly our friends' social output is summarized and highlighted for us, there are only so many hours in the day for us to express that we care. Today, the law of social sharing is a useful way to think about the rise of social computing, but eventually, reality will make it obsolete.