"Every day that these sites operate without recourse can mean millions of dollars lost to American companies, employees, and economy, and an ongoing threat to the security and safety of our citizens," said the RIAA's Mitch Glazier.
But the devil is in the details, said NetCoalition's Erickson.
"This bill reverses the policy that has been in place since the beginning of the Web," he said, "that Internet companies shouldn't be liable, nor should they be required to police or snoop on their users."
What's more, said Erickson, many members of Congress have admitted they do not fully understand the bill. Erickson said some have conceded they don't know what a domain name is.
Rep. Lamar Smith, the Texas Republican who sponsored the House bill, said Silicon Valley's concerns are largely hypothetical. Sen. Ron Wyden, D.-Ore., who favors a compromise bill, has said he plans a filibuster when PIPA comes up for its first floor vote.
Both the content providers and the Internet companies have lobbied Congress hard. So far, most committee votes on the issue have gone against the Internet companies.