Although we don't see many here at Middlesex North, some of the other registries of deeds in Massachusetts report a fairly regular level of recording activity by adherents of the "sovereign citizen" movement. The theory has something to do with the law that caused the US to go off the gold standard back in the 1930s. Adherents contend that by declaring oneself a "sovereign citizen" (or sometimes a "sovereign country") they are no longer responsible for debts that would be payable in US dollars.
The case in point is from Washington state. An accountant who advised and assisted a number of tax payers is seeking Federal tax refunds in the amount of debt they were purported to owe, was sentenced to 5 years in prison and pay $700,000 in restitution. A press release from the Department of Justice about the case is here. The FBI contends that the sovereign citizen movement has been closely affiliated with domestic terrorism and therefore closely monitors such activity.