A Twitter blackout aimed at protesting censorship on the social media site is sweeping the web as its proponents urge users to go dark Saturday.

The event was first announced and widely distributed early Friday morning by the Anonymous-affiliated, highly visible @Anon_Central Twitter account, which Tweeted the following message, which was retweeted all day Friday: #TwitterBlackout - I WILL NOT TWEET on Saturday Jan 28th for the whole day. #TwitterCensored #j28 -- lets roll! #RT #Share to support.

And it has since taken off, bringing users from all corners of the social media site together in a coordinated effort to send a message via boycott to Twitter that censorship will not be tolerated by its users, and that anyone who opposes censorship should boycott the site Saturday.

The blackout plan arose out of the Thursday announcement on Twiter's blog that the social-media giant will implement a policy under which it can censor Tweets on a country-by-country basis:

As we continue to grow internationally, we will enter countries that have different ideas about the contours of freedom of expression, the posting read. Some differ so much from our ideas that we will not be able to exist there. Others are similar but, for historical or cultural reasons, restrict certain types of content, such as France or Germany, which ban pro-Nazi content.

That aspect of the announcement was Twitter's way of prefacing the censorship policy that has the Twittervers up in arms:

Until now, the only way we could take account of those countries' limits was to remove content globally. Starting today, we give ourselves the ability to reactively withhold content from users in a specific country - while keeping it available in the rest of the world. We have also built in a way to communicate transparently to users when content is withheld, and why, Twitter continued. We haven't yet used this ability, but if and when we are required to withhold a Tweet in a specific country, we will attempt to let the user know, and we will clearly mark when the content has been withheld.

The announcement seemed to many Twitter users who follow the ongoing issue of protecting Internet freedom and First Amendment rights to be nothing more than yet another step toward the censorship of social media.

Twitter account @The99Percenters announced in a concise Tweet on Friday that it will be participating in the Twitter blackout: #TwitterBlackout We R protesting country by country Twitter censorship on 1-28-2012 I will be tweetless.

Twitter user @ItsSoDamien on Friday Tweeted his reason for joining the Twitter blackout in a dispatch that resonates with many of its participants: #TwitterBlackout Because this is not what I signed in for.

The censorship announcement by Twitter comes on the heels of a number of news reports revealing the extent to which the U.S. government is getting involved in the social media site's affairs.

In one of the most recent cases to emerge regarding Twitter censorship, The New York Times exposed on Dec. 19 that some American officials said the government was exploring legal options to shut down the Shabab's new Twitter account, referring to the @HSMPress account supposedly run by Somalia's Shabab militant group.

A profile image created specifically for the Twitter blackout event, featuring a jet-black background with the Twitter bird mascot's eyes and beak poking through the darkness, and the words twitter blackout in stark white, was adopted Friday by many users planning to participate in the protest.

Social media expert Jeff Jarvis called Twitter's new policy part of a slippery slope of censorship, according to The Associated Press.

I understand why Twitter is doing this--they want to be able to enter more counties and deal with local laws. But, as Google learned in China, when you become the agent of the censor, there are problems there, he said.

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