So, why then are these newfangled social networks taking root and growing so fast? What is the value add? What do we get out of it? And why are these ephemeral and immediate networks so powerful?

Well, like you said, none of this is new, but — to answer those questions and the one about Google — the keys to the digital realm are its ease and rapidity. It is much simpler for me to keep tabs with friends via online means rather than having to call every week or sit down to hand-write and mail letters to everyone. And obviously people were able to write thesis papers before internet search engines, but man! do they make it easier and faster than sitting for days at a microfiche reader in the library.

Good post, Dave. (You and I should write more…)