E.G if they want to get into games like powdertoy to moderate and sa-mp to ban the users that dont have a registered copy of GTA San Andreas, they're going too far and the internet will be fucked up in over 50%(that's how much piracy is).
Many blogs will be shutdown(including mine it has a ton of links to pirated game and music torrents), Youtube will have moderated content etc. etc.
Now if it's just block the DNS of torrent sites and the similar, i can still type the IP in, and if the ISP denies access i'll just swap site or ISP. btw i dont think they can tamper with ISPs in other countries unless theres some kind of agreement so unless SOPA shutdowns entire sites...then it's nothing but a pain in the ass we can live with.