The Secret History of Silicon Valley - Steve Blank (Gave the same talk to Twitter) (youtube.com)

This is a pretty famous talk, it was also given when I attended CIKM '08. He is a really interesting speaker.

Plus his book is a great read for all startups: Four Steps to the Epiphany. If you don't own it, you should check it out:

http://www.google.com/products/catalog?q=four+steps+to+the+e...