Mark talked at YCombinator's Startup School this weekend, and even he admitted that much of entrepreneurship and innovation involves not knowing what you're doing.

He also laments short-term thinking, which he attributes to Silicon Valley: http://techcrunch.com/2011/10/30/facebooks-zuckerberg-if-i-were-starting-a-company-now-i-would-have-stayed-in-boston/

Personally, I never thought of Silicon Valley as a place that encourages a certain type of thinking. Some people think short-term and others -- among them, Apple, Oracle, and Google -- think longer term.

Having the feeling that you don't know what you're doing is pretty universal.

Entrepreneurs learn by doing.

SV is all about knowing what's going on, knowing what's going to be longer-term competitive, knowing if 10 other startups that are already funded and already doing what you are doing, and not wasting your time trying to get VC funding for something that isn't VC-fundable.

I'd like to say that Mark's chat with Jessica was easily the best talk of Startup School. While I think Max's was the most introspective and refreshingly candid; Ashton was the best storyteller --- Mark proved that he's willing to "think different" and challenge the status quo. He was able to poke fun at himself (references to the Social Network), talk about what must be difficult topics (early days with Eduardo, etc.) and had great advice: focus on something you're passionate about.