This is the internet we're talking about. People flock to cool stuff that's free. For anything that isn't impossibly entrenched (Facebook etc.), it's an endless cycle of:
Awesome free thing ---> gets popular and increases in value based on popularity but isn't making much if any money ---> as popularity reaches critical mass, overhead increases and investor pressure to monetize begins ---> service gains baggage of monetization and becomes considerably less awesome ---> people flock to new awesome free thing that doesn't yet have that baggage simply because it's not far enough along in the cycle yet.
Snapchat just unveiled $0.99 for three snap replays microtransactions. Probably the beginning of its downward spiral.
I don't really worry about the social media or app stuff, where the primary cost is technological. Eventually bandwidth and computing power will be so prevalent that anything like that is worthwhile to enough people will be run p2p.
You can see it starting with stuff like friendica, obviously no where near mainstream yet, by it is perfectly feasible for these kinds of services to be run by the users.
The content producers may have an issue, but it seems pretty apparent to me that we have an oversupply of content on the web, which is part of the reason for the cutthroat internet ad market. Maybe we need for a certain percentage of these sites to die off so the audience can condense to a number that is financially sustainable, instead of using increasingly invasive advertising techniques to milk money out of a tiny splintered audience.
I have no problem with ads in general, and don't run ad blockers(I just completely avoid sites with annoying ads), but when sites argue that their right to advertise extends to running arbitrary code from an unknown third party on my device to spy on me, they can fuck right off.