Great video explaining Web 2.0
http://www.youtube.com/watch?v=6gmP4nk0EOE

and another explaining changes in how we think about, store and retrieve information due to digitisation:
http://www.youtube.com/watch?v=-4CV05HyAbM&feature=channel

both by Professor Michael Wesch 'the explainer' according to Wired magazine

Also, a lecture entitled 'An Anthropological Introduction to YouTube' at
http://www.youtube.com/watch?v=TPAO-lZ4_hU