Kind of interesting, but then what's the point of Facebook? Asides from invitations - which, perhaps naively, this friend did through a post in his feed - the only thing that I'd be interested by is maintaining a light-touch connection with friends who are overseas by looking at their posts in the news feed.
Biggest use cases for me has been events and groups.
1. Events: Facebook's provides a streamlined experience for hosting events and all my friends use it for birthday parties, house warming and so on.
2. Groups: Facebook's group experience is quite good and I am a part of 4 groups of like minded people that I get to have conversations with quite frequently.
Makes sense in terms of network effects I guess. I wonder where the tipping point is when enough people aren't on Facebook so people go back to other services and / or email.
