I don't see the issue with making a social network that's more focused on real-time, current irl connections. Snapchat has already used a similar model with decaying content to great success.

I think you're likely of a generation that's attached to the Facebook model where a social network is an ever-growing photobook/history of interactions with all your friends. Maybe that has a place, but I think it's worth being open to other ideas. And yes, maybe when someone dies, they're no longer part of this network in the same way they are no longer part of many other things in your life. I don't think that's inherently bad.