The watchwords for the vast majority of BDSM enthusiasts are these:
safe, sane, and consensual. You will hear these words mentioned at BDSM conventions, in BDSM publications, in
BDSM books, and in BDSM forums. The focus of the majority of BDSM in North American bedrooms is on an enjoyable and safe (both physically and mentally) experience for both parties.
The rising popularity of BDSM may be a result of the sexual repression that exists to a greater and lesser degree in our society, but I'm not convinced it is the sign of a "sick" society. It is an activity that brings great joy to many people, and it is an activity with does not involve anyone against their will or cause any permanent harm or even any temporary harm, since I would be very hesistant to call mild pain which is enjoyed harm.
Don't get all freudian on me, and I won't get all freudian on you. Okay?