There's no such balance of interests for the payment processors or ad networks under SOPA or PIPA: they simply have to block their accounts within five days of getting a letter, unless their accused customer writes back with a letter promising to come to a US court. A site like YouTube would remain protected under copyright law, but become extremely vulnerable to having its finances choked off by overzealous copyright owners under SOPA — imposing a huge additional cost on new startups that host user content and effectively undoing the flawed but effective protections for those services currently in copyright law.

That's just the first part. SOPA section 103 and PIPA section 4 require payment processors and ad networks to shut down accounts if they receive the right kind of letter from a copyright owner — a system modeled on the heavily criticized notice-and-takedown provisions of the current Digital Millenium Copyright Act that requires a service like YouTube to pull down infringing content after the copyright owner complains. That system has been abused on occasion, but it ultimately works because it allows YouTube to avoid direct responsibility for the actions of its users — it would have been otherwise sued out of existence.

(These rules don't apply to domains that end in .com, .net, and .org, which fall under US law — the government has been seizing US domains used for piracy since 2010 , and just seized 150 domains last month .)

SOPA is a law borne of the blind logic of revenge: the movie studios can't punish foreign pirates, so they are attacking the internet instead

Oh, but it gets worse. Much worse. SOPA section 104 offers legal immunity to ISPs that independently block websites that host illegally copied material without any prompting from the government. That's a major conflict of interest for a huge ISP like Comcast, which also owns NBC — there would be nothing stopping Comcast from blocking a foreign video service that competes with NBC if it could claim it had a "reasonable belief" it was "dedicated to the theft of US property." And indeed, Comcast is among the companies that support SOPA.

Now, you may have noticed that while all these rules are totally insane, they're all at least theoretically restricted to foreign sites — defined by SOPA as sites with servers located outside the US. That's important to know: at its simplest level, SOPA is a kneejerk reaction to the fundamental nature of the internet, which was explicitly designed to ignore outmoded and inconvenient concepts like the continuing existence of the United States. Because US copyright holders generally can't drag a foreign web site into US courts to get them to stop stealing and distributing their work, SOPA allows them to go after the ISPs, ad networks, and payment processors that are in the United States. It is a law borne of the blind logic of revenge: the movie studios can't punish the real pirates, so they are attacking the network instead.

SOPA's proponents argue that the bill will protect US citizens and corporations from the ongoing theft of property outside our borders; that the law is narrowly tailored to only punish those who profit from illegal content. Indeed, it's possible the notice-and-takedown system for payment providers could potentially resist abuse: unlike YouTube's reflexive takedowns, it's hard to see a credit card processor turning off a paying account just because it gets an angry letter in the mail. But that's just one piece of the puzzle, and the deep concerns about tinkering with the DNS system have never been adequately addressed by any of SOPA's sponsors or supporters.