What's needed is some kind of almost insurance scheme so that the long tail of content can be served up, but if a video goes viral, it doesn't become completely unavailable.

Needs care with adverse risk selection, because freeloaders who want cheap video bandwidth for god knows what will crowd around.

That's an interesting idea. Could default to slow performance served directly off your laptop, and if it goes viral the network automatically moves it to a CDN at no extra cost to you. As an extra bonus, whatever small fee you pay to buy in isn't a complete waste of money, because presumably you get value from the viral content of others, ie as a consumer of their content.