And the populations that consume the most leafy greens (and minimal calcium) are shown to have the least incidences of bone fractures and osteoporosis. Yeah sure Vitamin D helps but Vitamin K (found primarily in leafy greens, other green vegetables, and avocados - see the green pattern here?) and saturated fats are extremely overlooked.

http://www.ncbi.nlm.nih.gov/pubmed/11684396

And here's how excess consumption of milk (calcium and vitamin D) actually promotes osteoporosis...

http://www.4.waisays.com/ExcessiveCalcium.htm

To save you the reading, from what I understood and using the best of my ability to explain to you how too much calcium is bad for your bones is;

disclaimer this is not exactly how it happens but just so you understand what's going on in a nutshell

Imagine your bones are cylinders. There is a tiny hole on the bottom and a tiny hole on the top. In one of the holes calcium goes in; the other, calcium goes out. When your bone needs calcium, it draws it in from the input hole. When that calcium gets used up, it moves it out to make room for new, fresh calcium to do its work. Now if you're consuming too much calcium, then you're clogging up the input hole. When the old calcium is no longer needed, it still gets dumped out but new calcium can't come in because you clogged the input hole.

again that's not the exact process but just so you can understand why too much calcium is bad for your bone health

Want stronger bones? Eat more Vitamin K. Saturated fats help as well. So I guess if you're worried about it, just make sure you're eating enough greenery to compensate for the excess amounts of calcium that your body doesn't need. Vitamin K helps metabolize the calcium in your blood.

I suspect that it is D deficiency that is the issue here. Possibly along with Magnesium deficiency.

I think correlative, and that protein intake is not the culprit either. I think Dragonfly makes a good point about the D, as D is necessary for proper Calcium utilization. The data showing that dairy causes the body to excrete Calcium makes sense if you can't use all the Calcium you are consuming. It would be interesting to see if cultures with history of vitamin D deficiency also share similar rates of those diseases.

I think people often look for reasons to vilify dairy and it's gotten a bad reputation because it is not well tolerated by some people. I agree with Peat/Roddy here; if you don't tolerate dairy, you're the problem, not the dairy. I think this can be for a number of reasons including vitamin D. Then you can get into reasons about why you're deficient in D, including deficiency in A, K, and Magnesium. Also to Tony's point they would both agree that there can be some problems with processed dairy, and I know Danny Roddy does raw dairy (which would help someone with lactose intolerance as raw milk has not had its lactase destroyed by processing). Danny has also written specifically about bone density, so his articles there may be of interest to you.

EDIT: Here is a great article about K by Masterjohn: http://www.westonaprice.org/fat-soluble-activators/x-factor-is-vitamin-k2 that discusses, among much else, bones and vit D.

I think it is simpler than all of that. Sedentary populations do not give the body the correct stimulus to maintain lean mass. This includes bone density. People sit on couches all day and watch TV. It does not matter how much nutrition is consumed, if the correct stimulus is not provided, the body will not increase lean mass. Populations from developing countries do not live sedentary lifestyles. Studies have shown that people who engage in strength training or activities that regularly require them to lift 'heavy' weights do not experience a decline in bone density.