Funny thread...I've had those 'ooh, my eyes!!' moments myself - and it was an old guy's bony behind - I don't think I would have minded half so much if it was one of those younger, tight, male roadie behinds!
My bf also seems to enjoy the view- in my mind, I'm pulling and setting a good pace, only to find out, he's back there with a happy smile on his face! (I DO have a mirror, you know!)