The timely blog Teablogging has revealed its sources:

According to documents obtained by Teablogging by running a goddamned simple Nexis search on the internets, national Tea Party organizer, Top Conservatives on Twitter cofounder and TCOTReport.com publisher Michael P. Leahy has, over the past 16 years, amassed nearly $150,000 in state and federal tax liens, small claims court judgments and civil suits.

Teablogging has .pdfs of all the documentation. My own impression looking them over is that Mike thinks the rules are for everyone else. Why protest taxes if you think you're not required to pay 'em in the first place?