The Stop Online Piracy Act (SOPA) is stirring up a lot of controversy in the tech world. Companies that rely heavily on copyright protection call the bill piracy protection; those that rely on user-generated content call it censorship. The bill strengthens the U.S. Justice Department’s power to go after websites that host disputed copyright material — and could make sites such as YouTube and Tumblr that host such user-generated content liable for copyright violations.