Rebecca MacKinnon -- predictably -- is banging the drum about Western governments putting social media under surveillance and making the unjustifiable moral equivalence with authoritarians such as Mubarak.
To cut it short, I would refer her and others again to international law on freedom of expression -- US law is even more refined and helpful, but the arduously-negotiated text of Art. 22 and Art. 30 help you understand the restraints for Art. 19.
Rioting, looting, burning -- these are contrary to the UN charter and also the denial of other people of their rights.
* Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.
* (1) Everyone has duties to the community in which alone the free and full development of his personality is possible.
* (2) In the exercise of his rights and freedoms, everyone shall be subject only to such limitations as are determined by law solely for the purpose of securing due recognition and respect for the rights and freedoms of others and of meeting the just requirements of morality, public order and the general welfare in a democratic society.
* (3) These rights and freedoms may in no case be exercised contrary to the purposes and principles of the United Nations.
* Nothing in this Declaration may be interpreted as implying for any State, group or person any right to engage in any activity or to perform any act aimed at the destruction of any of the rights and freedoms set forth herein.