The lack of meaningful enforcement of patent, trademarks and copyrights has been amajor weakness from the beginning of our Republic. One early inventor of the revolver went broke when he sold the patent for what he thought was a large sum plus royalties but with the provision that he take responsibility for defending the patent. The court costs bankrupted him. It really is rather strange that if a thief steals the physical machine you constructed or purchased, law enforcement takes the lead in bringing them to justices and prohibits you from going vigilante. If the same thief steals the design for the machine you patented, law enforcement does nothing and insists it is your responsibility to persue the offender through the courts.
I tend to think SOPA may be an over reaction. As I mentioned we do not arbitrarily close down pawn shops that operate in good faith. Nevertheless, law enforcement recognizes there is a very thin line between pawn broker and fence. They monitor these operations closely and move in agressively when they are suspected of moving stolen goods. We should take the same approach to the internet.