A controversial topic, but I can see its advantages and disadvantages. The advantages are that certain medical conditions can be stored and read from the chip using a compatible scanner. It can also be updated to reflect any changes in the subjects medical condition(s). This would be useful to those who suffer from diseases such as diabetes, and currently wear bracelets, since an implanted chip cannot be accidentally removed and forgotten (unlike bracelets, which people can take off and forget about). Of course, the disadvantage is that minor surgery is required to implant the device and that it is foreign to the body, but many people already have implants such as heart pacemakers, and there are no ill effects from that.