If you haven't heard, there is now a link to snapped Femurs in woman who have been on these drugs for a few years. Not only that, it has been found to kill the jaw bone.
The following link below is just one of many reporting on this problem.
My own mother in law snapped her Femur and now will never recover fully. She fell from a standing position in her own drive way.
Explained from another site: These drugs stop the body from reabsorbing old bone. So there is major build up of bone material, but the old bone not reabsorbed is very brittle instead of spongy in the center, therefore creating extremely brittle bones.
These broken Femurs in women looked like they had been in major car accidents, but had happened just by walking or falling from a standing position to the ground.