Nit: Dunbar’s number is casually used in a way that doesn’t seem relevant here. It’s not true that we can only remember about 150 entities. People know many thousands of words. (It is true that there are limits on what people will remember.)
Dunbar's number is that ON AVERAGE people can only maintain 150 relationships. "maintaining relationship" is not the same as remembering or knowing the person's name. It is spending enough time with the person that you have an ongoing relationship, which is eased if you remember a number of details about them (job history, hobbies, birthdays, etc). On average matters because the number is about group size, not any on…
At about 300 or so, you'll "recognize" most of the group, but you won't know much about many of them, or really have a relationship.
And once the group is above that, you either need to have it hierarchical setup (you don't know all the members of the families at your school, but you recognize the parents, etc) or it just becomes a mash of smaller groups (no matter how you try to pretend it isn't).