SOPA

Well, this is a bit late to the party, but I'd like to mention that I oppose both SOPA and PIPA bills in all of their forms.

Ever try to kill a fly with a flyswatter? It's actually pretty hard. The fly sees you coming and promptly gets out of the way. Now, imagine the fly is copyright infringers (I'm not saying it is a small problem or something that should be ignored), and the bills are a wrecking ball, trying to kill the fly. Can the wrecking ball kill the fly? Yes, most definitely; however, it is unlikely: the fly is simply going to move out of the way. In the real world, a wrecking ball would impart so much collateral damage to anything around the fly that no sane person would ever actually use it to kill a fly. It isn't the right tool to deal with the problem; the consequences of something going horribly wrong is too high, and the chances of it actually doing what you want it to do are slim.

Due Process
These bills give almost* no due process to the takedown procedure. (*I am not a lawyer, and do not understand every nuance of the bill, so I'll give the bills the benefit of the doubt and use the word almost. However, many sites have said there is no due process in the bills.) If someone with the authority to issue these takedown notices has a problem with a website, their website will effectively be off the Internet for most people. This affects me directly since I use the web as a platform to talk about a controversial topic, Creation vs. Evolution. As a biblical creationist, I have enemies, known and unknown, who would very much like none of my arguments see the light of day. While these bills are mostly directed at piracy, the fact that there is no due process makes this scenario very threatening to my first amendment right.

Many others have covered the due process issue, including Ars Technica.

I'm sure Google has a plethora of information on the bills. Particularly, reddit had a great post on the issue, laying out several of the specific details on how these bills are downright dangerous.