Scribd, which has aimed to do for document sharing what Spotify has done for music, is protesting two bills in Congress, the Stop Online Piracy Act and the Protect IP Act, by making some of the words in documents posted to its site disappear.

The site allows its members to post documents they’re reading or discussing, and the company is worried that the two bills — if broadly interpreted — could result in its site being pulled from the Web completely.

Proponents of the measures contend that they are narrowly targeted at foreign sites that pirate copyrighted content, and will not stifle free speech. But they do contain provisions that would allow the Department of Justice to obtain orders to block certain sites believed to harbor infringing content.

Scribd and other Web services take issue with those provisions.

“Congress is pushing through legislation that threatens the future of the Internet,” said Jared Friedman, CTO and co-founder of Scribd, in a statement. “With this legislation in place, entire domains like Scribd could simply vanish from the web.

“That’s why we’re showing our users just what SOPA and PIPA could do to Scribd and other sites. These bills aren’t just dry acronyms; they’re a direct attack on the underpinnings of the web.”

Scribd visitors today will see words in the documents they’re reading fade away before a lightbox pops up on the site explaining the rationale behind the stunt.

As The Washington Post’s Maura Judkis reported, opposition to SOPA is gaining a foothold not only in the Web community, but also among recording artists who’ve found fame through the sharing culture prevalent on the Internet.

The songwriter behind the “Obama Girl” videos, Leah Kaufmann, has written her own anti-SOPA theme song, “Firewall.” She joins British rapper Dan Bull in musical protest — an interesting development because the recording industry is a main proponent of the measure.

Reddit, which has been working hard to get its own users to oppose the bills, is also encouraging the public not to attend movies this weekend because of the motion picture industry’s SOPA support, Judkis reported.

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