Love acronyms? Then this post is for you! SOPA is the Stop Online Piracy Act, a bill sponsored by Rep. Lamar Smith to prevent theft of American-produced content (and, notionally, other nations' content) via any of the classic means of accessing paid movies, music, and so on online--without paying for it. PIPA is the Protect IP Act, a bill designed to have a slightly broader sweep than SOPA with the intention of protecting goods that are copied by counterfeiters--anything from drugs to handbags. Both are massively controversial , hence the online protests today from names as big as Google and Wikipedia.
Detractors point out  that there are Constitutional issues at play here, and there is already provision under the Digital Millennium Copyright Act to prevent, and criminalize, this kind of piracy and counterfeiting. And also that U.S. law, as it stands, allows for seizure of online domain names that are connected to piracy--something that ICE has done many times already , sometimes wrongly  (and perhaps illegally). In other words, SOPA and PIPA  are moves to prevent piracy that are above and beyond existing measures--and are so sweeping in power they may "break the Internet " for billions of users inside and outside the U.S.
Here are some of the sites taking part in today's protest, to greater or lesser extents. It may be the largest online protest ever (assuming some of the lesser-known names taking part aren't simply gunning for positive PR):
- Wikipedia  (mostly inaccessible)
- Google (logo censored for U.S. visitors, link to protest info for everyone)
- BoingBoing (inaccessible)
A fuller list can be viewed via SOPAStrike's website .