Or alternatively, it would just drive their customers to go use one of the other dozens of search engines out there. Do you really think people are that attached to Google that they'd refuse to use any other search engine and go complain to the government rather than saying "hey, I wonder if I can find what I'm looking for on Bing or Yahoo instead?"?illas said:If Google goes down for a day that could kill SOPA stone dead...
That's probably the major reason why Wikipedia is doing this while these other major websites are making a token effort. Wikipedia, unlike sites such as Google or Newsgrounds, is more a non-profit based organization that runs off of donations (you know, the reason they have those big banners at the top of the website every so often asking for money?). But if a for-profit website that gets its money from ad sales or otherwise running like a real for-profit company were to try to do what Wikipedia is doing right now, they'd risk A) Ticking off their customers; B) loosing money; C) driving their customers to other websites that ARN'T doing a 1-day blockout, potentially running the risk of loosing that customer long term if they discover that they like the alternative better instead.
So Wikipedia probably figures they can get away with doing the blackout while these other companies that might have supposedly joined Wiki reasoned that the potential risks of the blackout were not worth it to make the same kind of political statement.