The brief history of social media is the story of astonishing 1% success stories amidst the 99% also rans - but with the critical qualification that the cost of failure has been lowered so far as to be almost irrelevant.  Clay Shirky points out that there is no recipe for success but defines three broad rules... "a successful fusion of a plausible promise, an effective tool and an acceptable bargain with the users."

"The promise is the basic "why" for anyone to join or contribute to a group. The tool helps with the "how" - how will the difficulties of co-ordination be overcome, or at least held to manageable levels? And the bargain sets the rules of the road: if you are interested in the promise and adopt the tools, what can you expect, and what will be expected of you?" The order of promise, tool and bargain is also the order in which they matter to the success of any group. Creating a promise that enough people believe in is, not surprisingly, the fundamental requirement!