Feudalism was a system of nobles and workers. In exchange for the fruits of the workers labour, the nobles provided protection and the use of land.
In this analogy, Mark Zuckerberg is the king, the rest of the nobles consist of the employees of Facebook and some of the shareholder. The workers are the daily users of Facebook, they work the land by creating content for their ‘friends’ and follower.
Facebook by its position owns the land, they set up the infrastructure, built the applications, and store the data. They also provide protection, they allow users to block those they don’t like, provide safe spaces (groups) and protect content within their walled garden. Facebook protects users data and keeps the site online so the workers have a dependable place to go. Facebook goes to war to gain land, by building cloned products or flatout buys the competition.
Through this relationship, Facebook has come to be worth around 300 billion dollars, all of which belonging to the nobility (with some overlapping users). Most of the users have gained no capital for their work, though they may value the intangible social capital.
Something to consider: Facebook is a company that has created a web application. They work to build it and keep it online, but Facebook is nothing without its users. In fact, it could be argued that the users are the value of Facebook, without them it would be 1’s and 0’s on a computer. Facebook maybe a fun way to spend time, but by using it, you are working for free.