A small taster of why SOPA et al will have a disastrous global impact on the internet comes from this article, which highlights exactly what will happen if such draconian censorship laws are passed.
Someone writes an article about the problems of SOPA/PIPA, and then Google gets a DMCA takedown request from someone who doesn't like the sound of the article, that means it is omitted from search results. The site was removed, despite the request being completely baseless.
Without a trace of irony, the offended party have demonstrated exactly why such an act should not be adopted. Thank you, offended party. Now go off and have a good read of how teh interwebz works and you'll see why you've just made things worse for you.
Edit: And as if by magic, we have another example within hours of the first.
Edit 2: Oh, this is getting silly!