The New York Times reports that as many as 400,000 non-profit organizations will lose their tax status due to a provision in a 2006 pension bill:
The federal legislation passed in 2006 required all nonprofits to file tax forms the following year. Previously, only organizations with revenues of $25,000 or more — or the vast majority of nonprofit groups — had to file.
The bill also allows the IRS to revoke status to organizations that have not filed for 3 years. LINK