The early facebook pretty much _was_ the MVP of a CRM for your peer group - you could share contact details across a private network, invite groups of people to events and receive reminders of those that you'd been invited to, send public and private messages to custom groups and get notified of birthdays. You got nice pictures to be able to remember who did what the night before too.

If they'd taken their development in a different direction they'd have fewer page impressions but something much more useful.