It was only two weeks ago that Twitter was protesting online censorship in the form of anti-piracy bills SOPA and PIPA. Now the social networking site faces a surge of opposition to its own censorship practices.

Twitter announced in a blog post Thursday that it will now block specific tweets on a country-by-country basis should the messages violate the laws of those countries.

One of the worries is that Twitter has been a powerful tool in the protest movements that have surfaced across the globe in the past year, whether in the Arab Spring or the anti-austerity protests in Europe.

The fear is that the new policy will limit its utility in such instances.

Users have responded by promising to boycott the site on Saturday, and the media has blasted the company for what it views as blatant censorship.

Forbes' writer Mark Gibbs dubbed the move social suicide and many others have chimed in to voice their objection.

The boycott of Twitter is being promulgated by the hashtag #TwitterBlackout -- not all that different from the #SOPABlackout tweets from earlier this month. In another case of overlap with the SOPA/PIPA fight, hacking network Anonymous seems to oppose the move. Not known yet is whether it will act.

It's doubtful that enough people will stop using the service to have an impact, nor would a brief Twitter shutdown damage its business. However, the threats are clearly more about sending a message than crippling the now ubiquitous messaging platform.

The site's reasoning for the change was stated in its blog post: As we continue to grow internationally, we will enter countries that have different ideas about the contours of freedom of expression. Some differ so much from our ideas that we will not be able to exist there.

Observers see this as Twitter caving to the power of oppressive and restrictive foreign governments. They don't want to anger those countries too much, lest they block Twitter.

To some, this is appalling. To others, it's just business.

Either way, Twitter finds itself on the other end of the censorship fight for one of the first times.

Welcome to adulthood, Tweeps.