This is not an act that should ever be undertaken with a random dude or at a random moment; you both have to want it, and you both have to be prepared. True Life: I imagine it could be painful with a lover who is not very considerate, or if you are uncomfortable voicing what you need. I would say don't engage in anal if you feel like you may need a bowel movement soon as that would increase the risk it will be messy.
I'm just not sure. Some men behold anal sex as the holy grail, and if they can just get their wives and girlfriends to partake, then the floodgates so to speak about sex would open in general.
Most of these experiences have to do with not following the above instructions: You have to listen to your body. Would you like to comment on this page? This is my favorite reason. Yes, I have actually heard this in my office more than once.