I think a lot of you underestimate multi-boxers. If anyone is familiar with the game Naval Action, it's a sailing ship game where you manually aim cannon while manually sailing in combat. My friend runs up to four ships by himself. Admittedly his accuracy and maneuverability goes down, but the sheer mass of fire, total armor, and ability to rotate ships in and out of combat gives him a huge advantage.
Edit to add: And that's just combat. He'll sail two massive trade galleons on two accounts while escorting with warships on the other two. Trades all resources to one account that is the master ship builder. There are a lot of industrial applications for multiboxing. Especially when you don't care that 3 of the 4 characters are poor peasants in rags feeding all of their wealth to your main character.