Zuckerberg's Facebook page gives a more detailed stance on SOPA and PIPA with Zuckerberg writing:

The internet is the most powerful tool we have for creating a more open and connected world. We can't let poorly thought out laws get in the way of the internet's development. Facebook opposes SOPA and PIPA, and we will continue to oppose any laws that will hurt the internet.

The world today needs political leaders who are pro-internet. We have been working with many of these folks for months on better alternatives to these current proposals. I encourage you to learn more about these issues and tell your congressmen that you want them to be pro-internet.

Zuckerberg also posted a link to Facebook's Washington DC page which has more information about the company's official stance on SOPA and PIPA.