I think that some of you are misinterpreting the quote. You're putting the period in the wrong place and dropping off the end of the sentence.

Quote Originally Posted by Caitlin
'The whole thrill of BDSM is letting someone take advantage of you knowing that they won't.'
While I'm willing to admit my own inexperience, I would venture that one of the guiding factors for a Sub is the perceived loss of control. The doc's statement does not end at merely with being taken advantage of, but that there is a risk of such, and the Sub trusts the Dom not to do so.