If it is properly secured by a bracket, it is extremely unlikely that a chandelier will fall and hurt someone. It is also a big insurance liability risk, so if you have a chandelier that may not be fitted properly, it is important to have it fixed right away. As long as the chandelier is installed correctly and the anchorings are in good repair, it's probably not very likely. At least without some severe external influences (i.e. human tampering, extreme neglect and disrepair, catastrophic weather or earthquake, etc.), a chadelier isn't likely to fall on someone standing beneath it.