> He made it exclusive. You had to have a .edu address to sign up so the people ON the network were initially only your peer group. You couldn't get in without that .edu address and therefore you WANTED to get in if you couldn't.
Don't forget that each college's network was segregated from each other's.
You couldn't view the full profiles of people at other schools unless you were friends with them, but by default, you could view the full profiles of everyone else at your school (you could set your profile to friends-only, but most people didn't back then). I know that I didn't care that everyone else on my network could see my home address and my phone number on my profile, because I knew that they were all classmates (or professors, but very few of them were on Facebook). After I graduated and networks became less prominent, I locked down my profile to friends-only.
Groups were restricted to single schools (and Pages didn't exist): this kept group sizes small and made them feel cozier. Pretty much every school had a group for most fandoms, and it was a big deal if you were able to be the person who got to create your school's group for your favorite subject. There were a number of groups that were basically memes; I forgot what they all were, but no real discussion happened in the group, and their only value was to be listed on your profile. They were classified as "Facebook Classics", and what would happen was that the meme would take off at one school, then the members' friends at other schools would notice them on their profiles and create versions at their schools, and so on. Again, there was some prestige in being the first person to spread the meme to your school.
And there were some college-specific things on your profile, too. There were fields for your class schedule, and you had a separate "mailbox" field for colleges that had dorms.