I remember e-mailing a friend of mine and quoting somebody's off hand remark I'd read in a paper about seeing "a Barbie doll in black corset hanging over a bar counter in Tennessee, upside down, ball gagged and her hands bound behind her back --- I have never seen that model here at home /in Sweden/" This girl buddy who got the mail was thrilled about the image, and in talking about it the next day we more or less admitted we were both turned on by this kind of damsel-in-distress stuff. Didn't go as far as either of us actually saying it went into our wishes for r/l sex though, I figure she could be turned on by being tied up - or by seeing someone else tied up in bed - but I haven't brought it up with her again. She looks great, I like her a lot and being tied up by her would have been hugely erotic (i once admitted to her that my feelings for her crossed over into love sometimes, but we both felt we should keep it at friendship level; she was very gentle about this).
There are others whom I am open with, but with them it took longer time to broach the subject.