As with any decentralized model, I think the key is examining what kinds of value the consumer can get that aren't provided by a more centralized monopolist-to-be. It's not enough to provide an ideological alternative: the product itself must be an inherently better alternative.

So many of these business models would be enabled by a truly decentralized social web. If the web itself supported transactions and interactions, it would empower completely new kinds of businesses that would be on a level standing with each other.