Like everything else, it depends. Who wants to know and why? In what context? I spend too much free time pondering this topic and have yet to see as in depth of a slideshow as this fresh preso from Marta Z. Kagan. True to form, she not only took the time to produce the slideshow, but published it at slideshare. Check it out below. And then maybe you can tell me what the f**k this social media business is all about according to you.