An intriguing hypothesis, first suggested by Tim Berners-Lee, is that the structure of online groups should conform to a power law distribution. We relate this hypothesis to earlier work around the Dunbar Number, which is a supposed limit to the number of social contacts a user can have in a group. As preliminary results, we show that the number of contacts of a typical Flickr user, the number of groups a user belongs to, and the size of Flickr groups all follow power law distributions. Furthermore, we find some unexpected differences in the internal structure of public and private Flickr groups. For further research, we further operationalize the Berners-Lee hypothesis to suppose that users with a group membership distribution that follows a power law will produce more content for social Web systems.@en