Twitter, championed as a tool of free expression during the Arab Spring, was facing censorship charges on Friday after announcing it can now block tweets on a country-by-country basis if legally required to do so.

San Francisco-based Twitter stressed the move in no way compromised its commitment to free speech, but the backlash was immediate with critics taking to the service by the thousands to tweet disappointment and outrage.

"This is very bad news," said Mahmoud Salem, the Egyptian pro-democracy activist and blogger who tweets using the handle @sandmonkey. "Is it safe to say that #Twitter is selling us out?"

"Yet another low for free speech," said Jannis Leidel, or @jezdez.

Some Twitters users called for a boycott of the service on Saturday, punctuating their tweets with the hashtag #TwitterBlackout.

Others questioned whether Twitter's move was related to a $300 million investment in December by billionaire Prince Alwaleed bin Talal of Saudi Arabia, a country with strong Internet censorship.

Olivier Basille, director of Paris-based Reporters Without Borders (RSF), expressed "deep concern" in a letter to Jack Dorsey, executive chairman and co-founder of Twitter, which has over 100 million active users.

"By finally choosing to align itself with the censors, Twitter is depriving cyberdissidents in repressive countries of a crucial tool for information and organization," Basille said.

"Are you going to block the accounts of Syrian cyberdissidents if the Syrian authorities tell you to do so?" he asked.

Basille questioned whether Twitter's move was motivated by a desire to enter China, where the service is currently blocked.

"Is it possible that one day there will be a sanitized Chinese version of Twitter that has been rid of any reference to the Chinese Nobel peace laureate Liu Xiaobo?" he asked.

In its blog post, Twitter said the ability to block tweets by specific country would allow the rest of the world to continue to see them.

Twitter pledged to be transparent and said it would post details of any removal of content to ChillingEffects.org, a public database of takedown requests.

"As we continue to grow internationally, we will enter countries that have different ideas about the contours of freedom of expression," Twitter said. "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," Twitter said.

Technology bloggers said Twitter, by giving itself the ability to block content selectively for legal reasons, was falling in line with practices already followed by other Web giants such as Google, Facebook and eBay.

Danny Sullivan, chief editor of MarketingLand.com, said "these types of censorship demands have long been placed against search engines like Google or anyone who hosts content.

"Twitter is preparing for potential demands in the way that Google already does, by alerting its users to when content has been withheld and providing information about why," he said on MarketingLand.com.

Twitter has already been removing content to comply with copyright complaints, Sullivan noted.

"What's new is that eventually, Twitter may expand to having staff based in other countries," he said. "That makes the company more liable to legal actions in those countries, so it needs a way to comply with those legal demands.

"Overall, there doesnt seem to be a particular reason to hit the panic button here," Sullivan said.

Zeynep Tufekci, an assistant professor at the University of North Carolina and a fellow at the Harvard Berkman Center for Internet and Society, said that far from promoting censorship, Twitter's move was a "model policy."

"Twitter's latest policy is purposefully designed to allow Twitter to exist as a platform as broadly as possible while making it as hard as possible for governments to censor content, either tweet by tweet or more, all the while giving free-speech advocates a lot of tools to fight censorship," Tufekci said.

"The idea that Twitter can just ignore court orders everywhere is not only unrealistic, it would result in more countries (trying) to block Twitter completely," she said on her blog. "The Internet is not a 'virtual' space, and cyberspace is not a planet which can float above all jurisdictions forever."

She said the plan to publicize where tweets have been blocked is a "level of transparency (that) should be the model for all Internet companies" and also a powerful tool for free-speech advocates.

Twitter able to now selectively block tweets
San Francisco (AFP) Jan 26, 2012 - Twitter said Thursday that it now has the ability to block tweets from appearing in a specific country if legally required to do so.

"As we continue to grow internationally, we will enter countries that have different ideas about the contours of freedom of expression," Twitter said in a blog post.

"Some differ so much from our ideas that we will not be able to exist there," the San Francisco-based company said.

"Others are similar but, for historical or cultural reasons, restrict certain types of content, such as France or Germany, which ban pro-Nazi content," Twitter said.

Twitter said that previously, if it was required to remove messages, it could only remove them 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," Twitter said.

"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," it said.

Twitter said it would post details of any incidents involving the removal of content to ChillingEffects.org, a public database of takedown requests.

"One of our core values as a company is to defend and respect each users voice," Twitter said. "We try to keep content up wherever and whenever we can, and we will be transparent with users when we can't."

China, notably, blocks Twitter, a situation which Twitter co-founder Jack Dorsey described recently as "unfortunate and disappointing."