There are some obvious things that go in this box, Twitter, facebook, mySpace, and a tools like digg. But way too many things are being thrown into the box with websites that are driven by users interacting with each other.
Part of it is hype. If you have a few minutes to feel like something really exciting is happening, watch this video that pretty much makes any successful website part of "Social Media."
The numbers these people bandy about are amazing, but why not talk about how many billions of people make phone calls, or write letters, or attend community meetings? When you start talking about the millions of people doing things online as if the Internet created communication, you miss the entire point.
It's not Social Media, it's people being social using the most ubiquitous medium -- the Internet. The Internet is an amazing communication tool. It combines audio, visual, text and a way of referencing information that's never existed before. But, this idea that everything you never did online before 2008 is somehow "Social Media" completely misinterprets what the revolution is.
Reading a book on your Kindle is NOT social media -- telling a friend about a book on Facebook is social media. Watching a video online is NOT social media -- I don't care if you found the link to the latest episode of The Daily Show from a friend, the site that shows the program is a traditional content publisher.
All of this is just accelerated communication and faster access to information. The fact that people are involved in creating that information and communicating with each other means the Internet is going to be filled with that kind of activity.
But let's be clear -- Twitter and Facebook are just how we use the Internet today. The revolution is far from over.