Two articles just published in Nature Genetics may explain why some men lose their hair, while others do not. One of the articles shows the complexity of the gene, where the baldness gene not only has more than one site, but it also is on more than one chromosome. There is a link between balding, heart disease, and other metabolic abnormalities as well.
The published journal articles themselves are not online yet (not sure if they will be freely available by the publisher), but there are a few summaries in the news that I found, linked below. Read the news items: