SOPA would destroy the internet as the nexus of free information that we know it to be. This would be a bad thing. Here's a video which explains how the big companies supporting SOPA are the ones who got us into this mess:http://www.youtube.com/watch?v=WJIuYgIvKsc&feature=player_embedded
Yes, this guy is really annoying. He's also right.
There's also a lot of flimsy logic in this thread regarding sales and piracy. Piracy does not translate into a lost sale. I can't speak to how it affects video games, but I can discuss how it affects music. The reality is that 95% of artists on major labels come out owing their record company about $10,000 regardless of whether or not you purchased their albums or stole them. This was true pre-Napster and is still true today. This isn't because of piracy, but because of the industry's business model, which has been in use since the 1920s.
The music industry is more alive today than ever, it's the record industry that's on life support.