Is a PhD needed after an MD or DO if one wants to pursue a research career?
Look at it this way; an MD says you are qualified to practice medicine, and a PhD says you are qualified to do research. In theory you could practice medicine without an MD (it'd be illegal in many countries but not having an MD does not mean you don't have medical knowledge), and likewise you could do research, especially part-time, without a PhD. 

Leaving semantics aside, having that degree significantly increases your chances of pursuing a career in a particular field. If you intend on leaving the clinic and devoting your time and energy to research I'd say that a PhD would be expected, when you look for jobs. Whether or not you can bypass that expectation with other qualifications would be speculation.

As it turns out an MD &amp; PhD combination is... uhmmm how to put it delicately..  "so money". :)

I say you put your hat in front of you, figure what you want to do, and go for it. Many doctors here (in Sweden) go for a double degree and it is definitely not something that's frowned upon. On the contrary, in many cases it is an additional merit for future promotions.