More about . . . drum roll . . .
You can download Fifty Shades of Grey right now– or stroll into a retail establishment and demand, in a loud and strident voice, that they provide a brown paper bag with purchase.
View my law blog if you want to know more, but basically, consent to all sorts of fun and not-fun things can be written, oral, or implied, by behavior or circumstance. Usually, this kind of thing is implied (!) — but remember that consent can always, always be revoked at any time. It’s not a great idea to wait until the, uh, last minute – but if it ain’t your cuppa tea you have every right to change my mind. (Don’t expect your partner to be real thrilled with that though.)
The only thing that could concern me about this kind of behavior is the potential for abuse. Sex is always emotionally risky, and sometimes physically as well. Sex appeal is great and everything, but KINDNESS is so important, and integrity as well. Just sayin’. Assuming you’ve got that, a bit of variety doesn’t seem so bad to me.