CPR (cardiopulmonary resuscitation) and "mouth to mouth" is still important as a last resort but in comparison with defibrillators this does not save as many lives.
Defibrillators are small hand held safe electronic devices that automatically diagnoses life threatening conditions and applies a treatment that can restart someones heart. It saves lives without further risk to the person you are helping or yourself. There are no real legal risks for you or your organisation (unless you are completely stupid and act in a grossly negligent manner).
I have signed up to this public e-petiton call for all public buildings to install defibrillators and train staff. This petition came about after the tragic death of teenager Oliver King and points out that it is not only older people who are at risk but 12 youngsters die every week from Sudden Adult Death Syndrome (SADS). The footballer Fabrice Muamba who dramatically collapsed in March was saved by a defibrillator.
Hat tip Jake Morrison