This TED video explains things very eloquently:
The internet has given global society an unparalleled freedom of expression and access to information that would otherwise be totally out of reach. SOPA, PIPA and ACTA threaten to destroy this whole infrastructure. They, and any subsequent efforts to police the internet so severely, should be challenged at every step to ensure that a middle way is found. Piracy needs to be stopped, or at least curtailed as much as possible, but the method for doing so needs to be approached in a more reasoned and objective way than the current proposals that are being circulated.