Wikipedia is protesting against SOPA and PIPA by blacking out English Wikipedia for 24 hours. SOPA and PIPA represent two US bills in the House of Representatives and the Senate respectively. Stop Online Piracy Act and Protect Intellectual Property Act are efforts to stop copyright infringement committed by foreign web sites, but in Wikipedia's opinion, do so in a way that infringes free expression while harming the Internet.
"They put the burden on website owners to police user-contributed material and call for the unnecessary blocking of entire sites. Small sites won't have sufficient resources to defend themselves. Big media companies may seek to cut off funding sources for their foreign competitors, even if copyright isn't being infringed. Foreign sites will be blacklisted, which means they won't show up in major search engines. And, SOPA and PIPA build a framework for future restrictions and suppression."
Wikipedia (and SPCR) urges US citizens to call your government representatives and tell them you oppose SOPA, PIPA and any similar legislation. For more information, please visit Wikipedia's SOPA and PIPA page
SPCR discussion on SOPA & PIPA