There are certainly many different reasons for getting an MBA. Some people go just because you can demand a much high salary when you graduate. However, many others go to develop their analytical skills, expand their knowledge base, and meet highly capable individuals who have similar interests. Furthermore, most people getting MBAs have been in the workforce for 5-7 years. They are not trying to start the next Apple. They have found a niche in business they like and wish to accelerate their development.
If you have already started a successful business, then why would you get an MBA? You wouldn't, but if you don't have a large network of capable friends, what better way to meet one than by going back to school?
I love participating in this HN community, but think the amount of MBA bashing that goes on here is just ignorant. People aren't successful because they have an MBA, but getting an MBA certainly doesn't make them less likely to succeed. It's silly to generalize then marginalize a group of people because they do not take the same approach as the hackers here to making money and succeeding. Not everybody was meant to be a hacker, and while the members of this community should probably not be looking at getting MBAs, its stupid to have a disdain towards people who do.