Had to give it my shot.

Interestly, but nobody else seems to have edited it, either.

Perhaps:
Social Media: electronic means that enable virtual communication and collaboration

The term “social media” will not be a term, as it will continuously evolve as the social community evolves with it.

A: Plural

Social Media references the shift of the means of mass communications from the hands of a privileged few into the hands of the masses - the interactive methods and processes by which people communicate and collaborate with one another, enabled through emerging technologies….

Now that that is out of the way, the Real Question is “What the hell do you do with them?”
I have answers, but I have to get ready to have coffee with you on campus this morning.

Really great thoughts, but I think your definition remains too long because it focuses on explaining the impact of social media. Of course that’s crucial important, more important really than the definition.

But a definition has to focus not on the impact of what something does but merely on what that something is by observing its formal characteristics.

You wouldn’t define “guitar” by first exploring all the genres of music that feature it prominently. You would define guitar as: a stringed musical instrument with a fretted neck and resonating body, most commonly found with six strings, played by plucking or strumming the strings across the lower bout while fretting strings along the neck.

Maybe, if you were writing a long dictionary entry you’d mention the modern guitar’s Spanish origins or predecessor instruments like the lute.

What you probably wouldn’t talk about is flamenco music, or the impact of electrifying the guitar, or the post Beatles guitar buying boom that dramatically expanded the number of guitar players in the world, or the explosion of rock and roll so closely associated with the instrument, etc.

All those things may be more important than a definition, all those things would be part of an encyclopedia entry. But they’re NOT a definition.

The impact of social media is so big, and so interesting, that it’s easy to begin a definition with what social media does. But I don’t think that gets us closer to a definition–in fact, I think that takes us farther away but taking us into the side streets on a map before telling us “you are here.”

The definition matters not so much for Net natives, end users, or even long time social media practioners, but it DOES matter for the industrial growth of social media. If you were a VP of biz dev at Newscorp and in advance of the MySpace acquisition Ruppert Murdoch asked you “what is this social media?” you’d need a meaningful short definition.

One other thought, I would submit that social media is not changing the nature of human relationships–those relationships are still built around love, hate, friendship, work, shared interests, family etc–instead it’s changing the methods and modes of human relationships.