I would have to say the Federal Reserve system. Even though the argument that it was built to bring stability to the economy, this is false. The Fed allows itself and banks to only hold 10% of reserve funds and then they can print the rest to loan out. Which means they are pyramiding debt. This is the largest scam in history and it is the biggest because they control the money supply which is essentially our whole economy.
Social security is just one piece of the whole pie. Since the government steals the social security money, the fed will just print more money to fund it. This will lower the value of each dollar.
Anyway I'm getting off subject.. the federal reserve is lend by private bankers and they are looking for a chance to control the worlds money supply, so they can continue their scheme world wide.