I think what people need to remember is that people at the end of the day need to be kept safe. If they are not, all we would have is mayhem in our world. Blocking access to these networks during times of riot is a good measure to stay safe.
Access to social media is an important forum for the sharing of information. It has too many important and legitimate purposes to justify a shut down, even in times of emergency. A riot or protest is not sufficiently dangerous to justify a derogation from the right to free speech.
It is crucial to remember that social media is just one tool. Just as it can be used to organize crime, it can be used to organize a positive response, or help family members monitor the safety of their loved ones.
The government should never be allowed to block communication cables. This is a violation of our freedoms of assembly and our freedoms of speech. It will also make communities very unsafe. If someone innocent is caught in an unsafe situation like a riot, then they should be able to communicate with others in order to maintain or reach safety.
We should not block access to social networking during riots. It would be stupid to do this. Many people rely on these sites to communicate with family and friends. Some schools are even placing homework assignments on some of these sites. Blocking them down would do more damage than good.