I remember reading about a tech company 20 years or so ago (cant remember the name or industry) that attributed their success to splitting divisions in two when the head count exceeded 600. 600 was the maximum size where everyone knew everybody's name.

My experience is that 100 is a very good size to join. It's small enough that an individual can have an impact, that everyone knows who you are, that stock options mean something, and that you get paid every month.