Thousands of web sites are blacked out today. Most of the sites that are blacked out are ones where you might find discussions of what is going on in the world. These are the sites at greatest risk of being taken offline under SOPA, Internet censorship legislation currently being considered by the U.S. Congress. If that legislation passes, important web sites will disappear not just for one day, but for months or years at a time, and without any advance warning.