Social media has already played a key role in the case of George Zimmerman, who is charged with second-degree murder in the shooting death of a 17-year-old African-American, Trayvon Martin. Zimmerman, who claims he shot Martin in self-defense, has excited comment and argument across the political spectrum, much of it online; now defense attorney Mark O'Mara is establishing an official Web site and social media presence for his embattled client.

Law enforcement officials have always faced a balancing act when it comes to their public image, needing to appear tough (on the bad guys) but helpful and friendly (to law-abiding citizens). Social media can help with both tasks, as well as facilitate important functions like disseminating information to the public during emergencies, posting alerts for missing children or fugitives, and so on.

In last Sunday's New York Times magazine, Sherry Turkle, a psychologist and professor at M.I.T., wrote an interesting and thoughtful article, titled "The Flight from Conversation," lamenting the ways technology -- social media and mobile devices in particular -- has (ironically) made human beings less social. For one thing, they allow us to isolate themselves from our surroundings, including other people, enveloping ourselves in another, virtual world. They also deceive us into thinking we are having real conversations, when in fact we are just trading little scraps of text and carefully-chosen images -- while keeping each other at arm's length. …

A new social network launched by Google Ideas in partnership with the Institute for Strategic Dialogue is targeting (perhaps that's a poor choice of words) a very niche audience -- ex-terrorists and the former victims of terrorism. The network, www.AgainstViolentExtremism.org, is intended to fight terrorism by allowing interested parties to share information about preventing the growth of violent radicalism among young people.

The former director of the U.K.'s Government Communications Headquarters has co-authored a report for Demos, a think tank, calling for enhanced surveillance capabilities to combat criminals and terrorists using social media -- but also warning that rules need to be in place to protect legitimate use by ordinary citizens. The warning comes as the British government considers new laws that would allow law enforcement to force Internet service providers to hand over records that could be used to identify individuals engaged in illegal activity.

There are social networks targeting people dealing with a whole range of ailments, physical and psychological, and it certainly makes sense to create a forum (separate from Facebook and Twitter) for people to discuss sensitive topics like health problems -- something many would probably prefer to do anonymously, with a sympathetic and supportive audience, and out of the general public eye. This week brings the launch of another -- AnxietySocialNet, for people suffering from anxiety.

Invisible Children's "Kony 2012" video was an unprecedented viral success, having achieved over 100 million views. Now, Invisible Children is planning a "Cover the Night" event calling for continued support for the U.S.-assisted manhunt in East Africa.

Sports and social media is a natural fit, given the communal nature of fandom and the myriad fine points of strategy and stats. Two new social nets are launching this week: JockTalk and SportGrit.

The 2012 summer Olympics in London will be the first fully "social" event in the history of the games, thanks in part to an aggressive social media strategy pursued by the International Olympic Committee. The latest addition is a social media platform, the Olympic Athletes' Hub, that's intended to bring together Olympic fans and athletes and concentrate social media resources for both.

Health care organizations, including hospitals, health insurers and pharmaceutical companies, lag far behind consumers in social media adoption, according to a new Pricewaterhouse Coopers report titled "Social media likes healthcare: From marketing to social business," based on a social media survey of over 1,000 U.S. consumers and 124 members of the eHealth Initiative (eHI) -- a national association of industry organizations focusing on health information and technology. While that finding isn't particularly surprising, given institutional inertia and the volume of regulation they have to deal with, PwC points out that health care orgs are neglecting a major channel for patient …