Dunbar's number it basically says that the most amount of people that you can maintain stable social relationships with is 150
Dunbar's number is a theoretical cognitive limit to the number of people with whom one can maintain stable social relationships.
Morten Hansen's fantastic book on Collaboration in which he states that the real value of collaboration and of networks doesn't come from strong relationships and networks but from weak one's.
To know what the most important virtue of our age is we need to have at least a basic understanding of our age. Our era is becoming increasingly characterized by uncertainty. Fortunately or unfortunately, more than a cursory elucidation of our situation is beyond the scope of this essay. There are geopolitical, economic, technological and environmental trends worth mentioning. When the more philosophical portion of this discourse arrives I will argue that the virtue of wisdom underlies the meaningfulness and efficacy of all other virtues, and this in broad strokes is primarily due to (1) the aforementioned instability in our surroundings ; (2) the relationship between the deontological and virtue; and (3) the nature of agency itself. Whether uncertainty itself can provide an ethical foundation for us to elaborate on will be a separate question, and finally I speculate on where wisdom leads us in the context of a philosophy that is politically active and not doomed to irrelevance to and by the larger population.