Eh.. I don't know, maybe they've been consulting and guiding startups since before you were born?
They've even written an excellent book on starting a business called "Starting Up" (http://www.scribd.com/doc/4505824/Mckinsey-Starting-Up-Busin...)
Anyway, I don't think that the problem with Dutch startups is ambition. It is lack of action taking. If I look at people with awesome and ambitious ideas, they almost never go out and persue it full time. They also almost never try to find a cofounder. If they do, usually it's a group of friends that go at it part time.
So perhaps what we need to convince people of is that it's not so risky to stop what you're doing for a year and pursue a startup idea full time. The Netherlands is actually a very startup friendly country, people just don't know it. They don't know about tax advantages and subsidies available to entrepreneurs. Banks make it seem like getting money is hard.
BTW how did you manage to write a blog post about startup culture in Amsterdam without mentioning Bubbleconf? (http://www.bubbleconf.com)