I came across this video on the Fallon Planning blog. It's actually a series of videos called The Common Craft Show. They seek to explain Web 2.0 in the most simple ways possible. And in my humble opinion, they are brilliantly done. The one below explains social networking. Check out the rest of them here. I promise they will not disappoint. Perfect for a client [or parent] looking to understand what all the fuss is about.