Social networking does something to people, intoxicating them with near-zero accountability for impulsive behavior protected under a banner of free speech. Fierce defenders of the social media revolution think that because this technology is novel, somehow it should be afforded a special layer of protection. Social media empowers people, but it shouldn't make free speech apply to all forms of the 'fire in a crowded theatre'. Thankfully there are policy makers and courts who still feel that inciting violence, organizing illegal activities, causing riots, partaking in slander and libel, or harassment and abuse is wrong and/or criminal in nature regardless of the medium of communication.
New forms of 'fast and wide' communication technology have effectively armed common citizens with an information warfare tool. This is fine, but handle with care. Like any real tool of value, it can cut you. This is not a free speech issue, it's one of safety. When BART wants to shutdown communications due to threat of riot and crime, it's their right to do so. When Philadelphia wants to put a curfew in place to stop flash mobs, they are protecting the citizen. When authorities in London want to curb-stomp looting they should be able to do things like shut down riot tweeters. When the NYPD runs an intelligence group to hunt down terrorists and criminals on Facebook and Twitter, it's their right to do so - in fact, it's THEIR JOB to do so. If you are dumb enough to put your personal information on the 'net and then commit crimes, fair play (as Lulzsec has learned). Social media companies have a responsibility to work with government, law enforcement, and private authorities to ensure that they aren't enabling damage. Terrorists using Twitter are still terrorists.
When someone falsely claims a bomb threat, they are committing a crime. When they do it on Twitter, they are still committing a crime. As two people just learned in Mexico, putting it on Twitter doesn't make it legal. And, several men were jailed in the UK for using Facebook to incite violence during the riots. And today it's common for cases to be won against cyber bullying. Yes, embrace social media, but don't think that entitles people to be assholes.