muddiver:Becoming a Divemaster moves you into the "professional" catagory and opens you up to liability if a diver with in 1/4 mile of where you are diving has an accident. Being trained in how to lead, teach diving and prevent accidents can be held aginst you in court if some mad eyed, greeving family member snares you in some sort of liability suit over a dive accident. Same holds true for thoes trained in emergency medicine or advanced first aid that do not act if within the vacinity of a medical emergency.
This is a common observation that crops up from time to time and my understanding is that it is simply not true (diving one that is I dont know about medical). You need to have a 'Duty of Care' to the person(s) who had the incident,
Unfortunatly is it probably also true that in the land of the Ambulance Chasers you will need to hire a lawyer to tell the sueing lawyer to 'wake up and smell the coffee idiot theres no liability here...'
Also you should be careful using the word Teach as a DM you do not 'teach' you may demonstrate but only an Instructor will 'Teach'