What is SOPA?
The Stop Online Piracy Act (SOPA, H.R. 3261) is on the surface a bill that attempts to curb online piracy. Sadly, the proposed way it goes about doing this would devastate the online economy and the overall freedom of the web. It would particularly affect sites with heavy user generated content. Sites like Youtube, Reddit, Twitter, and others may cease to exist in their current form if this bill is passed.

What is PIPA?
The Protect IP Act (PIPA, S. 968) is SOPA’s twin in the Senate. Under current DMCA law, if a user uploads a copyrighted movie to sites like Youtube, the site isn’t held accountable so long as they provide a way to report user infringement. The user who uploaded the movie is held accountable for their actions, not the site. PIPA would change that – it would place the blame on the site itself, and would also provide a way for copyright holders to seize the site’s domain in extreme circumstances.

The Electronic Frontier Foundation laid out four excellent points as to why the bills are not only dangerous, but are also not effective for what they are trying to accomplish:

The blacklist bills are expensive. The Congressional Budget Office has estimated that PIPA alone would cost the taxpayers at least $47 million over 5 years, and could cost the private sector many times more. Those costs would be carried mostly by the tech industry, hampering growth and innovation.
The blacklist bills silence legitimate speech. Rightsholders, ISPs, or the government could shut down sites with accusations of infringement, and without real due process.
The blacklist bills are bad for the architecture of the Internet. But don’t take our word for it: see the open letters that dozens of the Internet’s concerned creators have submitted to Congress about the impact the bills would have on the security of the web.
The blacklist bills won’t stop online piracy. The tools these bills would grant rightsholders are like chainsaws in an operating room: they do a lot of damage, and they aren’t very effective in the first place. The filtering methods might dissuade casual users, but they would be trivial for dedicated and technically savvy users to circumvent.

Source: http://sopablackout.org/