To follow up to the parent, there is a lot more to B-school then just to network. From common MBA-bashing that takes places on HN it seems that that many people fail to grasp the difference between building a product and building a company. If you want to build a product - MBA may not be necessary, but if you want to build a good company, an MBA will be a great help along the way. With all aspects of running a business covered in one class or another, you at least have an understanding of the issues you'll run into.

An MBA doesn't provide you a road map, it gives you a framework of how to approach business questions and an understanding how simple decisions cascade down to all aspects of a company (hr, accounting, operations).