I don't think it will increase your earning potential as a physician other than the business savvy that you would hopefully gain as a part of your education. If you did end up in the position of administrator, especially in a large group, your earning potential could be greatly increased. But would you want to be an administrator and not a physician?
As to the DO vs. MD portion of the original post, this has been addressed time and time again, there is no "real" difference between salaries. The physician with the best combination of residency training, experience, and #of procedures billed for will make the most money.
A regular MBA who is good at his job has a lot higher salary ceiling than most physicians, so if money is your main interest, then skip med school. This isn't a career to get into if you want to become rich. You will be comfortable, but most likely you will never be rich.