Many of Silicon Valley's most successful entrepreneurs and executives are warning of the dangers of the controversial Stop Online Piracy Act in a new open letter to Washington, D.C.

It's signed by Google co-founder Sergey Brin, Twitter co-founder Jack Dorsey, PayPal co-founder Elon Musk, Yahoo co-founder Jerry Yang, among others. It will appear as a paid advertisement in The New York Times, The Washington Post, and other newspapers.

The letter's timing is no coincidence. Rep. Lamar Smith, a Texas Republican who drafted SOPA, has scheduled a committee vote tomorrow on a slightly revised version and still highly controversial version--call it SOPA v2.0.

SOPA will "give the U.S. government the power to censor the Web using techniques similar to those used by China, Malaysia and Iran," the letter says. Chris Dodd, the chairman of the Motion Picture Association of America, recently invoked China as a model, saying that "when the Chinese told Google that they had to block sites" the company complied, according to a report at Variety.com. Dodd backed away from that comparison in a speech (PDF) yesterday, saying it's unfair to compare shutting down "foreign rogue sites and the policies of repressive governments."

SOPA represents the latest effort from Hollywood, the Recording Industry Association of America, and their allies to counter what they claim to be rampant piracy online, especially from offshore sites such as ThePirateBay.org. It would allow the Justice Department to seek an order making allegedly piratical Web sites virtually vanish from the Internet. (See CNET's FAQ on SOPA.)

In advance of tomorrow's committee vote, opposition is mounting from Internet engineers, Web companies including Facebook, Twitter, Google, and Zynga, and civil liberties and human rights groups. Harvard law professor Laurence Tribe says SOPA violates the First Amendment and "should not be enacted by Congress."

Rep. Darrell Issa (R-Calif.) told CNET that he's planning to offer amendments to SOPA that would "reduce" the discretion of the U.S. attorney general. Rep. Jared Polis (D-Colo.), a Web entrepreneur who like Issa is on the House Judiciary committee, said in an interview with CNET that he has similar concerns about the Justice Department and is also planning to offer amendments.

Keep reading for the text of the open letter.

An Open Letter to Washington

We've all had the good fortune to found Internet companies and nonprofits in a regulatory climate that promotes entrepreneurship, innovation, the creation of content and free expression online.

However we're worried that the PROTECT IP Act and the Stop Online Piracy Act--which started out as well-meaning efforts to control piracy online--will undermine that framework.

These two pieces of legislation threaten to:

* Require web services, like the ones we helped found, to monitor what users link to, or upload. This would have a chilling effect on innovation; * Deny website owners the right to due process of law; * Give the U.S. Government the power to censor the web using techniques similar to those used by China, Malaysia and Iran; and * Undermine security online by changing the basic structure of the Internet.

We urge Congress to think hard before changing the regulation that underpins the Internet. Let's not deny the next generation of entrepreneurs and founders the same opportunities that we all had.

Marc Andreessen, co-founder of Netscape and Andreessen Horowitz

Sergey Brin, co-founder of Google

Jack Dorsey, co-founder of Twitter and Square

Caterina Fake, co-founder of Flickr and Hunch

David Filo, co-founder of Yahoo!

Reid Hoffman, co-founder of LinkedIn

Arianna Huffington, co-founder of The Huffington Post

Chad Hurley, co-founder of YouTube

Brewster Kahle, founder of the Internet Archive and co-founder of Alexa Internet

Elon Musk, co-founder of PayPal

Craig Newmark, founder of craigslist

Pierre Omidyar, founder of eBay

Biz Stone, co-founder of Obvious and Twitter

Jimmy Wales, founder of Wikipedia and the Wikimedia Foundation

Evan Williams, co-founder of Blogger and Twitter

Jerry Yang, co-founder of Yahoo!