Are dairy products, specifically milk, an effective dietary source to help prevent osteoporosis or could they cause more harm than good? Should we, as a society, be drinking more or less milk?

Are dairy products, specifically milk, an effective dietary source to help prevent osteoporosis or could they cause more harm than good? Should we, as a society, be drinking more or less milk? Are there better dietary choices for calcium or should we all be taking calcium supplements? Please elaborate on your reasoning with your research.
Support your opinion with valid research.