This is important. I got an undergrad business degree and I got a nice background in accounting, finance, marketing, and to a lesser extent IT.
When I think back on it, either it doesn't seem useful or I've forgotten the useful bits (had some great classes on branding that taught me a lot more than what you'd learn from reading blogs or articles on it; but I couldn't write an insightful paper on it now).
But then, I've dealt with people with no background in these things and watched them make some pretty stupid mistakes that could've been prevented with basic knowledge of these subjects. (I once got a sick feeling--justified--when asking a partner about our finances after he insisted on handling them, and getting an email where he referred to "the books" in scare quotes).
On the MBA side -- the MBA program at my alma mater has placed several of my friends in jobs that were a big jump in salary and growth potential from where they were coming in -- and none of them were bankers.
I heard someone say once that an MBA is a great preparation for an entry-level CEO job, but no such job exists. That's why real world experience matters; not only do you gain perspective that will benefit your MBA education and post-MBA career, but it also helps you "know thyself" so that you don't bother with an MBA if it's not the right move for you.
Last thought: business education doesn't really prepare you for entrepreneurship, but entrepreneurship can help you benefit from a business education. Best example would be an entrepreneur who has had some failures and moderate successes, but now has the experience and skills to command a 100K+ salary and is ready to further prepare (or for the cynical, get credentialized) for a job at that level.