The Monkeysphere for humans is about 150 individuals: the number of people you think of as being in your social group.
I think it only fair to say that the phrase the Monkeysphere came from Cracked.com, though it’s based on serious scientific research done at the University of Liverpool:
Humans are primates, too – so do they fit into the pattern established for monkeys and apes? This is the key question which Robin Dunbar sought to answer by using the same equations to predict human social group and clique size from neocortex volume. The results were… ~150 for social group size, and ~12 for the more intimate clique size. He subsequently discovered that modern humans operate on a hierarchy of group sizes. (Research Intelligence)