A large-scale social experiment in the form of a MMOG to recreate dynamics of feudalism, possibly intensified by being bet upon.

• There are a fixed number of castles in the game. Each castle has one owner at a given time.
• A castle provides a steady income to its owner. This is the only source of in-game money.
• A group of players can jointly attack a castle. If they defeat the current owner and any allied players in in-game combat, a pre-specified member of the attackers becomes the new owner.
• The game does not provide contract enforcement mechanisms. You can recruit an attacking army by promising them a share of the castle's income, but they only have your word you'll follow through.
• (optional) A monthly payout is distributed in proportion to in-game wealth. If the game were widely played, and wealth were highly concentrated, this could be very significant for some. Failing this, soft messaging such as leaderboards encourages amassing wealth as a goal.

The idea would be to see the coalition dynamics that play out. My suspicion is that people would at first try egalitarian coalitions to share income evenly, but over time things would get more and more hierarchical as established coalitions started admitting 'junior partners' on worse terms.