Although the House and Senate bills are similar, SOPA is the more extreme of the two. It defines a "foreign infringing site" as any site that is "committing or facilitating" copyright infringement, whereas PIPA is limited to sites with "no significant use other than" copyright infringement. More details on SOPA and PIPA are available through the Library of Congress website.
Arguments for and against SOPA and PIPA
Opponents of SOPA and PIPA believe that neither piece of legislation does enough to protect against false accusations. As the Electronic Frontier Foundation argues, provisions in the bill grant immunity to payment processors and ad networks that cut off sites based on a reasonable belief of infringement, so even if claims turn out to be false, only the site suffers. "The standard for immunity is incredibly low and the potential for abuse is off the charts," says the EFF.
Meanwhile, sites that host user-generated content will be under pressure to closely monitor users' behavior. That monitoring already happens on larger sites such as YouTube, but it could be a huge liability for startups, the EFF argues.
Some progressive pundits have argued that media companies are trying to legislate their way out of what's really a business-model problem. "As we've seen over and over again, the most successful (by far) 'attack' against piracy is awesome new platforms that give customers what they want, such as Spotify and Netflix," TechDirt's Mike Masnick writes.
SOPA and PIPA supporters argue that prophecies of a broken Internet are overblown. Cary Sherman, CEO of the Recording Industry Association of America, writes that SOPA clearly defines infringing sites based on Supreme Court holdings and the Digital Millenium Copyright Act, and requires rights holders to follow a strict set of rules when trying to get payment cut off to an infringing site. False claims, Sherman argues, "can result in damages, including costs and attorneys' fees."
Sherman also points out that previous actions against infringing sites, such as the MGM vs. Grokster case in 2005, triggered similar doomsday predictions from the tech industry, yet digital music innovation has flourished since then.
Who's for SOPA and PIPA, and who's against?
Representative Lamar Smith (R-Texas) is the author of SOPA, which is backed by 31 cosponsors in the House. Senator Patrick Leahy (D-Vermont) wrote PIPA, which has 40 cosponsors in the Senate. ProPublica has a visualized list of supporters in both the House and Senate.