There are already limitations on committing crimes, terrorism, fraud, making threats, etc. over the Internet. You can actually go to jail right now for Internet stalking. In fact, there are already laws against piracy (stealing intellectual property).
There is no need for this law and it can only harm the free exchange of information.
I’m reading up on SOPA now. I doubt I’m the only one who hasn’t heard of this, or much about it, before.