If you’re read my The Law of Social Media essays or presentations, you probably know there have been few serious cases yet establishing law specifically targeting social media. One can apply basic principles to predict what courts will do, but so far there are only a handful of reported decisions that say anything at all about social media.

That does not mean nothing happened in 2010 in this rapidly evolving area. In my view, the most important developments are reflected in these four cases:

1. The Food & Drug Administration’s citation of Novartis for Facebook content that lacked required pharmaceutical side-effect warnings and disclaimers, and the agency’s subsequent delay in release of social media “guidance” for pharma until Q1 2011. The case illustrates that heavily regulated industries face special risks and burdens in structuring social media marketing campaigns.

2. The assertion of jurisdiction by the National Labor Relations Board over “protected activity” of employees (discussing working conditions, for instance) on Facebook, even where the company is not unionized. This shows that, although equal employment issues still dominate employers’ use of social media in hiring and firing, there may be limits to which companies can penalize workers for their social media posts if the content is work-related.

3. The New Jersey Supreme Court’s decision in in Stengart v. Loving Care Agency, Inc., reversing the older, black-letter rule that employees have no privacy interests at all in employer-provided email systems.

4. The decision just days ago by the U.S. Court of Appeals for the 6th Circuit in United States v. Warshak, holding that the 20-year old Stored Communications Act’s approval of warrantless seizure by the government of user emails is unconstitutional under the Fourth Amendment. This is the first judicial opinion that extends “reasonable expectations of privacy” from snail mail and the telephone to email, using a principled and thoughtful constitutional analysis.

Since the advent of email, the telephone call and the letter have waned in importance, and an explosion of Internet-based communication has taken place. People are now able to send sensitive and intimate information, instantaneously, to friends, family, and colleagues half a world away. Lovers exchange sweet nothings, and businessmen swap ambitious plans, all with the click of a mouse button. Commerce has also taken hold in email. Online purchases are often documented in email accounts, and email is frequently used to remind patients and clients of imminent appointments.

In short, “account” is an apt word for the conglomeration of stored messages that comprises an email account, as it provides an account of its owner’s life. By obtaining access to someone’s email, government agents gain the ability to peer deeply into his activities. . . . If we accept that an email is analogous to a letter or a phone call, it is manifest that agents of the government cannot compel a commercial ISP to turn over the contents of an email without triggering the Fourth Amendment.

And as my friends at SiliconANGLE have observed, the same rationale should apply as well to emails stored in “the cloud” or other Web-based email systems, like Gmail and Hotmail.

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So there you have ’em.  Not quite as interesting as the worst-dressed actress and best cinema films lists we’ll see over the next few days, but (perhaps) a bit more relevant to our daily activities on social networks and the real-time Web.