[nwah1]

For text, computing resources are cheap enough that it can be entirely non-profit or run by independent bloggers, etc. Wikipedia, blogs, IRC, and sites like HN don't require all that much and could be financed without ads if they chose to be.

Video, particularly HD video, absolutely requires ads or subscriptions. Social networks could probably be built atop WebRTC and run in a federated way, more like IRC... but image or video sharing would start to demand significant resources.