The Lazarus book is a good overview. My general gist on this is: If you don't know why you would want both degrees at this point, don't get them. There will be plenty of opportunities later to get an MBA if you should find it necessary or helpful in advancing your career or managing your career goals.
An MBA is not a magic degree. It is a baseline degree that involves an basic understanding of business concepts (finance, accounting, operations management, marketing, strategy, etc.) and depending on the school that you go to, a wide variety of in depth knowledge of various aspects.
Since virtually every institution offers MBAs (it is no semblance of the strict regulation that medical schools undergo to stay accredited, despite the AACSB accredition stamp), a top MBA is qualitatively considered to be very different than a run of the mill MBA in the business world. Does that mean that it makes a difference in your career? Maybe, maybe not. If you want to be an IBanker at Goldman Sachs directly out of business school, unless you already know someone working there, it's going to be tough outside of the core schools that they recruit at (<10 schools nationwide) to get a job. If you want to advance in your hospital admin, University of Phoenix may do the trick to get your ticket stamped.
The other thing to consider between a top MBA and a non-top MBA is the networks that you make. At the top schools you interact with people who generally are seeking high profile positions around the country and may provide valuable business contacts in the future in the usual B-school feeders (IBanking, Consulting, Brand Management, etc). Smaller schools tend to provide more regional contacts, but may be stronger in some industries than others (e.g. Rutgers has a good pharmaceutical marketing program, but certainly would be on anyone's top 10 list of Business schools).
As to when to do the MBA: There is a good reason why most top 10 MBAs generally only admit students with at least 3 years of work experience. The more you already know, the better you are able to utilize those experiences to apply to the conceptual frameworks they are giving you. Thus, if you are going to do high school then college then a MD/MBA I would probably argue that you would have gotten more out of it by doing your MBA later, especially after you have some hospital experience so you know where the warts are first hand. Obviously situations will vary.
Oh, and to one other poster's comments: yes, no business people seem inordinately impressed with an MD. They assume that it means that you are insanely smart (as opposed to just willing to work insanely hard). Either way, having both, occasionally will open up a door that isn't available to you, although sometimes it will close a door, since they may question why you are leaving medicine.
For one MD's journal of business school you can read:
http://www.businessweek.com/bschools/mbajournal/01mathew/1.htm