I'm gonna just put my 2 cents worth in.

While I don't belive that my wife has "witheld" any sex, I'm sure that when she was mad at me, or upset over something I've done(or more appropriatly NOT done) I'm sure that she'd not wanted to have sex.

This also holds true to any feelings of depression or stress that have effected her moods as well.

I guess what I'm saying is that with the women that I have been romantically involved with use "witholding sex as a punnishment".
( I really faught off the urge to use Pat Benatar's "Sex as a weapon" pun there)