A recent discussion about what critical mass is for a social network site started me thinking about the difference between tipping points and critical mass. Technically both are defined in similar words (sometimes considered synonymous), but they do have different connotations.

A tipping point can be defined as “the culmination of a build-up of small changes that effects a big change”. It is many times tied to an event that adds a missing catalyst or critical amount of energy to achieve a self sustaining reaction. In Gladwell’s book (The Tipping Point) he refers to the mechanics of this being related to “three agents of change” which he calls “the Law of the Few, the Stickiness Factor, and the Power of Context”.

On the other hand, critical mass might be defined more clinically as an “an amount or level needed for a specific result or new action to occur”. For a general purpose social network the chances of a person being interested in or staying in that social network are greatly increased if they already know someone in that network.

Since according to Dunbar any person should be able to keep relationships with about 150 friends, you can surmise that a critical mass would be 150th of the total number in the community. For example if you take a network of 300 million people (US population) and divided that by the maximum size of each persons social graph (150 people) we come up with 2 million people. At that point everyone is likely to have at least one friend that is using the network.

This is of course simplistic, but in practice works as a good rule of thumb for determining when you have achieved critical mass. If we consider smaller regional social networks (e.g. Los Angeles) this rule can be applied as well. For 12 million LA metro residents we would get a critical mass at about 80,000 for a general purpose network.

The problem with simple critical mass calculations is that most social networks are not general purpose. In narrow demographics the effect of connectors and mavens is exaggerated. In order to cost effectively reach the tipping point within a narrow demographic you must be very conscious of Gladwell’s agents of change and how they are related to your objective.

Now here is the fun part. One path to a tipping point is to capture mind share in your demographic. Thanks to search, by influencing the domain mavens and connectors you can effectively control and capture a much wider demographic. If you manage to become popular with people who review a product, you can dominate information and opinion related to a product in the marketplace.

Capturing definitive mind share can be achieved with a much smaller number of people. With a demographic of 800,000, and a critical mass may require 8,000, pervasive mind share may be achieved by influencing the most influential 80. In creating a social network for a specific demographic it is critical to create a strategy that effectively leverages Gladwell’s agents of change to to achieve your goals.