When the question of how big a community should be, a number sometimes given as a maximum is 150. This is Dunbar's number, a suggested limit to the number of people with whom one can maintain stable social relationships.
In practice, unless the community is very isolated, 70-80 people is a better limit. Why? In addition to live-in residents, a community will have peripheral members that hang out at the house, such as former housemates, boarders, and residents' friends and romantic partners. These peripheral members effectively double the size of the community.
In the Berkeley student co-ops, houses with 50-70 residents often have the strongest house cultures, while the two houses with 120-150 people are so large that residents don't know all their housemates. This pattern also appears at the Austin co-ops, and may have been an issue at Pacifico in Davis as well.
It is worth noting that Dunbar's number was originally derived from pre-industrial farming villages, where the community involved not just living together, but working together. Members of such a 150-person community would not have outside jobs or social contacts outside of the 150.