It's a small world. And six degrees of separation is real. I don't think it should be a problem if, over time, I date people within the same social circle. When I think about it, it almost seems inevitable that it would happen. We're attracted to people who are like us. It's natural to flock toward those who share similar interests and beliefs. Chances are if I like a guy I'm going to also like his friends...because they're probably a lot alike.
I've only had issues dating in circles when it comes to black men. There's a level of insecurity and ego that I don't come across with other races. I first noticed this racial discrepancy when I was in high school. I was "talking to" someone I really liked. We hadn't had sex yet. We went to different schools. In the early stages of getting to know each other I continued a casual sex relationship I had with a guy he happened to go to school with. I didn't know they knew each other. I'll call the one I was dating Jason and the fuck buddy Andy. After Jason found out about Andy he started treating me like I was tainted and undateable. I was extremely caught off guard. I felt like I hadn't done anything wrong because Jason and I weren't exclusively together.
In college I met more open-minded people. I had a fling with a dude in my friend group whom one of my best girlfriends had hooked up with a year or two prior. Time is an important factor to consider in the fragility of these situations. It helps to let some time pass before getting involved with someone a friend used to date/fool around with. It's also helpful to have your friend's blessing before getting with his or her former flame. Without acknowledging the overlapping you risk looking like you're being shady.
Another important thing to consider is the potential you see in the new romantic relationship. If your friend doesn't give you his/her blessing, is it worth possibly ruining a friendship? I say only if you feel like you could fall in love with the girl or guy you're interested in. If you just want to get your "back blown out" it's probably easier to find someone else to fuck.
A couple years ago I was seeing someone I really liked. One day he casually mentioned bringing his friend to the club I worked at. I was mad at first. I thought, Why doesn't he care if his friend sees me nude? We talked it out. To make his point he said to me, "I don't like you because I think I'm the only guy who's seen you naked." I think what he said sums up my thoughts perfectly. We aren't dating each other based on sexual history, or who's seen us with or without clothes on. At least we shouldn't be. There are more important things to consider like if a person is ambitious or kind to others. I would love to see more men overlook when someone he knows has already had sex with a woman he's interested in. In the mean time I'll be leading by example.