Generally the people in your social group is much more likely to belong to the same telecommunication system as you do. And you don't care nearly as much otherwise. Someone in Nepal will care a lot less when Facebook gains 100,000 more users in Italy than when those new users are in Nepal itself.
We can make a much better approximation of the real usefulness of the network by individualizing the law to each user, i.e. "...the square of the number of connected users of the system (n2) in your relevant social group."
Notice that since an individual has "cognitive limit to the number of people with whom one can maintain stable social relationships", this modified law also place a much sharper limit on a network's usefulness by Dunbar's number. http://en.wikipedia.org/wiki/Dunbar%27s_number