Let's be clear: learning about those lessons will take maybe, at most, a month or two of reading a couple of books, reading PG's essays, and reading a few of the blogs written by great entrepreneurs and VCs. That's it. An MBA probably does teach you this - it just doesn't need to take two years and XYZ thousand dollars. There's a lot of fluff in an MBA that's just not necessary for a startup.

The fact also remains that the vast majority of people I know who got an MBA did it for the network, not for the education.