Depo-Provera Safety

Majikthise blogs a London Globe and Mail news release that is getting almost no media attention in the U.S.: Pfizer's injectible contraceptive can cause irreversible bone loss, putting users at significantly increased risk for osteoporosis. FDA has just required Pfizer to put a black box warning on Depo indicating that it should be used only if no other birth control mechanism is adequate. Where are the discussions of the evolution of this warning?