There's not much we can learn from Yahoo's first fatal flaw. It's probably too much to hope any company could avoid being damaged by depending on a bogus source of revenue. But startups can learn an important lesson from the second one. In the software business, you can't afford not to have a hacker-centric culture.
(Have you ever read Graham's Hackers and Painters? It's really good. It'll validate your unhappy feelings about high school ... and make you all obsessed with Lisp.)