We often think of communities as organic creatures, which come into existence and grow on their own. However, the truth is they are fragile blossoms. Although many communities surely germinate and bloom on their own, purposefully creating communities can take a tremendous amount of hard work, and one factor their success ultimately depends upon is their numbers. If a community is too small you'll often have insufficient critical mass to sustain it.
A blog on social software, collaboration, trust, security, privacy, and internet tools by Christopher Allen.
In my initial blog entry on the Dunbar Number I presented some statistics on group sizes based on the online game Ultimata Online. In it you could clearly see the power-law (pareto) curve, with diminishing returns at around 150, with most groups being 60 in size: More recently, Nick Yee and other researchers at the PlayOn Blog have been researching the behaviors of players in the popular World of Warcraft online game.