Dr. Peter Gott, a well-known doctor, syndicated newspaper columnist and author, is advising his patients not to take Fosamax, Boniva, or Actonel:
" ... they – especially Fosamax – can cause a serious side effect called mandibular necrosis, or decay of the jawbone. Consequently, I have encouraged my patients to stop taking these drugs and have been searching for an appropriate substitute." (spokesmanreview.com)
Update: The above link no longer appears to be working.