Congress is working on legislation to stop online piracy, which is a good goal for people trying to protect intellectual property on the internet. However, the bills in the works invite abuses that would enable censorship and cripple free speech, which is a bad thing for people trying to protect intellectual freedom on the internet.
The Stop Online Piracy Act (SOPA) and PROTECT IP Act (PIPA) are bills written with vague language that would give corporations and government the power to shut down websites over accusations of copyright infringement, even if the site could never be held liable for infringement in court. This is bad news for all your Justin Bieber cover videos and Garfield/Legolas crossover fanfiction.
You can find out more about SOPA through Wikipedia, which is, by the way, blacked out today in protest of SOPA and PIPA. Their page includes more detailed information about these bills, what they could mean for the future of the free internet, and what you can do about it.