Human Embryonic Stem Cells

Ever heard of stem cell therapy?  These are usually human embryonic stem cells that are cultured and injected into the body to heal a patient.  Doctors and researchers are raving about this breakthrough in science because according to them, even the most serious diseases can be cured.  While I think this is great because it can cure a lot of diseases, some are questioning its effectiveness and safety.  Well I can't see why it won't be safe.  The cells will be taken from your own body; cultured and allowed to regenerate; and then given back to you to replace damaged cells.  I'd be reluctant if the cells were not mine.