As I noted yesterday, organizers of the SOPA strike got a boost when Wikipedia said they would shut down operations tomorrow, in protest of anti-piracy legislation that could constrain their business. In place of normal content, Wikipedia founder Jimmy Wales said he would put up phone numbers for members of Congress and try to “melt the phone lines” in Washington with calls in opposition to SOPA, and its Senate companion PIPA.

SOPA looks to be in a holding pattern for the rest of the year, but the Senate will still vote on PIPA next week, so activists plan to harp on this until the bills truly die.

Tiffiniy Cheng, one of the co-founders of Fight for the Future, the main grassroots activist hub against SOPA, said in a statement that “SOPA supporters are still going to try to win this: They’ll tweak the existing bills to show that they are being responsive to criticsm, but will leave in language that will capture domestic websites — breaking the architecture of the Internet while stifling free speech. Or worse, they could try to delay votes on the bills until people aren’t paying attention anymore.” So the fight goes on.

MoveOn announced today they would join Wikipedia, Reddit, Mozilla, Boing Boing and others in the SOPA strike. In a statement, MoveOn Executive Director Justin Ruben wrote:

Congress is playing fast and loose with Internet censorship legislation that would have people like Justin Bieber thrown in jail for uploading a video to YouTube. The Internet censorship legislation could severely restrict free speech, and put a stranglehold on one of the most innovative, job-creating industries of our time. MoveOn is joining the massive website blackout because it’s critical to preserve an open internet that enables our members to engage on issues they care about. Members of Congress, both Democrats and Republicans, would be wise to take a step back and reconsider their support for this reckless legislation.

Overall, 5,000 websites are on the record on “going black” tomorrow to protest the Internet censorship bills. One site that won’t join them is Twitter, which opposes the anti-piracy bills, but whose CEO called the protest “silly.”

In a tweet, Twitter CEO Dick Costolo called Wikipedia’s plans to pull the plug on its website “foolish” and “silly”.

Via Twitter, Radar correspondent Alex Howard asked Costolo, Google’s Eric Schmidt and Facebook’s Mark Zuckerberg, whether they would have the ‘cojones’ to follow in Wikipedia’s protesting footsteps. “That’s just silly. Closing a global business in reaction to single-issue national politics is foolish,” Costolo replied.

Google and Facebook did not comment. So Wikipedia is the big fish in the SOPA strike, and it’s a bit sad not to see more solidarity here and a flexing of muscle, just because one day of profits would have to be sacrificed in the exchange. The stakes of this legislation passing are far greater than that.

Nevertheless, enough sites will participate in the SOPA strike that it should get the attention of Internet users, and by extension, Congress.