RSS is a good example. In the simplest form my proposed social network structure could be seen as RSS feed of all the social web that is stored in a decentralized database. The main feature is that the posts can be 'liked' or 'upvoted' by users (domains).
The sudden idea is to separate metadata and content on different services and merge them only for viewing and interaction. Then users can selfhost content and request its distributed social metadata (upvotes, emotes, other people's comments etc) dynamically without easily losing control over the content itself.