I remember an episode of HBO's Real Sex where there was a sex shop in Germany that has workshops that teach women techniques of using a strap-on to butt-fuck their husbands/boyfriends well. The owner of the sex shop said that the majority of his business's strap-on trade is due to straight couples. I have been with more than a few straight bi-curious guys, or those who just wanted to see what the 'gay thing' was all about, who experienced an epiphany when their prostates were explored by me for the first time. They had never had a female partner who had probed that very sensitive area and never had any idea that they had such an erogenous zone. A few shot their loads from prostate stimulation alone, but most of them got a bit of help from some, uh, 'lip service'. Almost all of them admitted that the ass-play was something that they had really enjoyed, and that surprised them.