Purpose of the Swan

A full season after its destruction, the purpose of the Swan remains mysterious. It's not a Skinner box, but why two people had to enter the numbers is a mystery. What were they preventing? And why did it have to be people? Why not a computer just automatically doing whatever it is that the Swan did?

Here's my theory. We know that after Desmond used the fail safe that contact with the outside world has been cut off. Well my theory is that the Swan was keeping communications with the outside world open. Something about the Island makes it difficult or impossible to leave. Somehow, Dharma figured out a way to open it up. This is what the Swan did. It counteracted the effect which cut off the Island. The reason that the Swan had two people in it rather than just using a computer is because the two people were a failsafe. If something happened, they could refuse to input the numbers and shut down access to the Island. So, for example, if the Hostiles took over, then the Swan would be able to isolate them on the Island. This would explain why the Swan had such a large stockpile of weaponry and food. It was meant to be able to hold off an enemy, possibly for an extended time. I think that Kelvin was the last member of the Dharma Initiative. After the Purge the Dharma Initiative retained control of the Swan and used it as leverage to have some control over the Others.