The Web is buzzing Wednesday about the Stop Online Piracy Act, the bill that was debated in a morning House Judiciary hearing. Here’s a quick cheat sheet on the issues around the bill.

What is SOPA?: The Stop Online Piracy Act, introduced last month by House Judiciary committee chairman Lamar Smith (R-Texas) is a bill aimed at — surprise, surprise — stopping online piracy. In part a companion bill to the Senate’s “Preventing Real Online Threats to Economic Creativity and Theft of Intellectual Property Act,” (Protect IP), the bill could punish Web companies that host unauthorized copyrighted content such as movies, songs or software.

Critics of the legislation say that it could increase lawsuits against Web companies or give the government too much power to shut down sites for hosting the content.

Who is for/against it?: You may be surprised at who’s teaming up on either side of this debate. The Motion Picture Association of America is, unsurprisingly, one of the lead voices supporting the bill, but it is joined by allies from the pharmaceutical industry, the U.S. Chamber of Commerce and, yes, even the International Association of Firefighters, who say that piracy saps the tax dollars that support emergency services.

The list of opponents is even more varied, from Web firms such as Google (which has made a huge push against the bill) to progressive rights groups who say the bill could stifle free expression online to tea party activists who say that the measure gives far too much business-strangling power to the government.

Why all the buzz?: The bill is buzzy not only because it has the potential to affect a wide range of industries, but also because it’s got a lot of momentum behind it. Smith has said that he intends to markup the bill by the end of the year.

Despite the controversy, the bill has a great deal of bipartisan support, with 21 members joining Smith in co-sponsoring the legislation.

How does it compare to the Senate’s bill?: The Protect IP Act passed the Senate earlier this year. Sen. Ron Wyden (D-Ore.) placed a hold on the bill, citing concerns about its potential to “muzzle speech and stifle innovation and economic growth.”

SOPA, critics say, goes even further than the Protect IP Act, because it grants the government even broader powers to go after Web sites hosting copyrighted content. Internet openness group Public Knowledge said that “SOPA is significantly worse than its Senate cousin” because it lowers the barriers to who can be considered liable for IP theft, saying that sites that don’t do enough to prevent piracy — such as search engines — can also be held liable for infringement.

How big of a problem is piracy?: Setting aside the debate of how it should be legislated, there’s evidence that online piracy is a serious financial problem for the country. The Chamber of Commerce estimates that U.S. companies lose $135 billion a year to counterfeiting and piracy.

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