I too would worry about some one who hurts another just for the "heck" of it. On the other hand I've never consented to be "punished" either, although there have been cases where they just assumed I had.

A lot of this seems to come down the distinction between S&M and D&S. My thing is being hurt for the sexual pleasure of another, submission follows on from that. So it works best for me when there aren't any outside issues, such as "punishment" as some sort of motivation. Mutual pleasure doesn't work that well either. As a switch I feel I have an understanding of a sadists desire to "be a tyrant in the bedroom" (as deSade put it), so sensual pain might be a fun why to spend time with a person but it's not addressing my core sexuality.