2. As Alexis said, it introduces penalties to US citizens for using foreign-hosted sites deemed to be in violation of the act.
3. the notion that it only applies to "wholesale" piracy is garbage. that might be what the NBC dude thought it would mean, but there's no way to unambiguously define what is wholesale piracy and what is casual or inadvertent piracy, and it is ultimately up to the courts to decide who the law applies to and who it doesn't. If some judge wanted to, he could probably use SOPA to take down just about any website with user-generated content. a good law isn't one that's broad and over-reaching and you just hope that it's implemented fairly. a good law is one that is specific, targeted, and difficult to abuse.
4. the point that i'm disappointed that nobody made: the pirate bay is a .org (and nominally a .com), which technically makes it a US site. the NBC guy's prime example of why we need SOPA is immune to SOPA.