Once again it is under the guise of stopping astroturfing. However as is explained by grassrootsfreedom.com , "The grassroots legislation, simply stated, is unconstitutional. It is nothing more than some with vested financial and political interests trying to violate the First Amendment rights of others."
Another group, DownsizeDC.org, is also working against this dangerous legislation. They have set up an e-mail your Congressman tool.