There are a number of ways of paying for a social network. Among them:

- Ads

- Subscriptions

- Loss leader for another product

- Microtransactions

Facebook does ads.

Subscriptions hurt network effects.

Google+ ran into a brick wall of network effects.

Nobody uses Flattr, and it's hard to imagine people paying a buck for video filters or other premium features.

It'd be great to solve the problem without building another Facebook, but my best guess is that if Facebook goes down someone else builds another system basically identical to Facebook and we all have this conversation again 10 years in the future.