I was forwarded a disturbing link about Pam containing Butane and Propane. Well of course, like a good skeptic and scambuster, I did some quick research. First looking at the link I saw that the picture showing the ingredients was actually ISOBUTANE and Propane as propellants. Yes isobustane is different from butane.
Propane is actually odourless and colourless in it's natural state (they add the smell for safety reasons for the barbeques). It is also non-toxic and used as a propellant in a lot of "aerosol" cans.
Obviously if one ingests or more appropriately inhales it directly there are potential problems of increased heart rate, dizzyness, headaches.... Ingested, it might induce vomiting, nausea, internal hemorrhaging. Again, you have to consider the dosage and this is only through large dosing of propane by itself.
Isobutane is used a food additive and propellant as well. Relatively harmless. It is flammable. Also do not inhale (like a druggy) as it may cause dizzyness, irregular heartbeat, asphyxiation. Of course too, this is direct inhalation (of the gas itself...not Pam). Using a one second burst on a pan is perfectly safe as the exposure is so minimal with it being away from the nose, the duration of the spray, and the well ventilated space.
This link is a MSDS (Material Safety Data Sheet) which is a document about the risks of substances (see WHMIS).
In other words, this is some of the best information you can have about the dangers of a substance.
So relatively speaking, Pam is very safe. There does seem to be some valid concern over the use of Pam on pots and pans in regards to it building up over time and therefore reducing the non-stickness of the pans.
Pam is also good for less calorie intake.
I don't use cooking sprays myself as I have found them not to my liking in regards to performance over time and taste. But this choice is not made because of any health concerns or supposed dangers.