Opponents say that it violates the First Amendment, is Internet censorship, will cripple the Internet, and will threaten whistle-blowing and other free speech actions. Opponents have initiated a number of protest actions, including petition drives, boycotts of companies that support the legislation, and planned service blackouts by English Wikipedia and major Internet companies scheduled to coincide with the next Congressional hearing on the matter.

Why it matters to you. Why this matters to sites like Wikipedia.
Laurence H. Tribe, a Harvard University professor of constitutional law, released an open letter on the web stating that SOPA would “undermine the openness and free exchange of information at the heart of the Internet and, it would violate the First Amendment.