Bix at Fanatic Cook has a post on calcium and dairy consumption as regards to protection against broken hips from thin bones (osteoporosis). Or rather the lack of protection!
I’ve worried before that most paleo diets could be deficient in calcium because they don’t include milk products. Osteoporosis in adults or inadequate bone growth in kids are about the only significant problems you might see if that’s the case.
Bix quotes Harvard professor and pediatrician Dr. David Ludwig:
“Humans have no nutritional requirement for animal milk, an evolutionary recent addition to diet. Anatomically modern humans presumably achieved adequate nutrition for millennia before domestication of dairy animals, and many populations throughout the world today consume little or no milk for biological reasons (lactase deficiency), lack of availability, or cultural preferences.
Adequate dietary calcium for bone health, often cited as the primary rationale for high intake of milk, can be obtained from many other sources. Indeed, the recommended levels of calcium intake in the United States, based predominately on balance studies of 3 weeks or less, likely overestimate actual requirements and greatly exceed recommended intakes in the United Kingdom.
Throughout the world, bone fracture rates tend to be lower in countries that do not consume milk compared with those that do. Moreover, milk consumption does not protect against fracture in adults, according to a recent meta-analysis.”
Another article mentions Dr. Ludwig:
People with a high-quality diet — those who get adequate protein, vitamin D and calcium from things like leafy greens, legumes, nuts and seeds — may get little or no added nutritional benefit from consuming three servings of dairy a day, Ludwig argues.
Hmmm. Wonder how he feels about grains. Sounds paleoish so far.
I’m just about ready to stop worrying about calcium.
Steve Parker, M.D.
Paleo Diabetic 
It always seems obvious, after the fact: Paleo people didn’t get much chance for “milk” after infancy. If they could tolerate it after infancy. Dark greens, etc. would be the perfectly sufficient natural choice. And people don’t need excess calcium, and it’s even worse to get calcium unless there is sufficient D3 and K2. And that means “fermented” vegetables and various proteins… and most people now do not realize the absolute need to have those nutrients in their diet. Dairy can provide calcium, and that’s maybe ok, so long as it ends up where it’s supposed to go. And not as plaque in arteries and on heart valves.