Despite the fact that I'm just this side of detesting screencasts, there were 5 seconds of insight at the end of Jon Udell's whirlwind overview of del.icio.us. Of course since it's continuous media, I can't go back and find the exact quote, so I'll paraphrase, regarding how languages develop from pidgin:
All you need is an environment that let's people speak to each other, hear each other, and adapt their behavior to what they hear.
Recommended if you don't know much about del.icio.us.