From the lessons learned during the 20+ years I've been involved in online community and social networking (starting with CompuServe forums where I was a participant), I have formed what with some fun I call Phil's law.
Phil's law simply posits a central weakness at the heart of online social networks.
Phil's law: There's an inverse correlation between the time it takes to scale a social network and the durability of that social network
In other words, the faster it scales, the higher the probability it will fail.
Improvements in technology allow online social networks to scale increasingly faster building an inherent weakness right into their DNA. Phil's law is a challenge to a much-cherised belief in the power of technology-based networks - and the supposed advantage brought by the scale effects of technology. Seen as a strength, I'm suggesting that these scale effects are not only temporary for social networks but are the reason for their eventual failure.
What is the force behind Phil's law?
Trust. Phil's law comes from the inverse correlation between speed of scale and trust. Trust grows at the speed it has grown for thousands of years and not faster. Think of trust as the speed of light for the universe of social networks - i.e. no social network can grow faster than the speed of trust.
Unless a social network grows slowly and organically offline, then it will not be durable.
A quick history of online social networks
Think of the increasing speed that social networks have formed online and then fallen - CompuServe's forums, AOL's forums, all the various late 90s communities, Friendster, MySpace and yes, Facebook. Phil's law predicts that Facebook will fall. Facebook - because of its speed of scale - has a higher probability of failure than did these earlier social networks at their height.
A corrollary: breadth makes Phil's law more invisible until...
A corollary to Phil's law is that the bigger and broader a fast-growing social network, the more invisible is its underlying weakness - until one day it falls seemingly overnight. New members joining hide the disaffection of veteran members until a critical point is reached when all of it sudden the network is abandoned.
A counter-example: YPO
Compare this history to the history of YPO - the Young President's Organization - which began in 1950 and has slowly grown to now more than 17,000+ Presidents and CEOs around the world as of 2011. YPO has very high retention rates and long-term durability. It continues to grow. But to its benefit, it's not primarily an online network. Members meet offline in local groups that are member-led.
- Phil Terry
Phil's law does *not* mean that online tools cannot be a supplement for social networks nor does it mean that all social media elements or businesses are doomed to fail. User reviews, Twitter (the new digital news service), LinkedIn (the jobs board for recruiters) are all going to be around in some form or another. Twitter doesn't require trust - it's a replacement for PR Newswire. LinkedIn also doesn't require trust - it's a replacement for older job boards (and I think they should embrace that rather than overinvest in groups, etc.). User reviews are critical for retail and other industries like travel. These are just a few examples of elements and companies that have social elements but are not primarily social networks.