Although the approach to this post is a little strange, from personal experience I can say that it does happen.
After I was divorced and before I met Mrs. WS I dated quite a bit for a while. Mrs. WS and one other woman were the only single women I had sex with during this time. I wasn't looking for them, but they found me. For instance, I met a Meg Ryan look-a-like at a club one night. She was out with friends. We hit it off really well and she told her friends I'd give her a ride home. Which I did. When we got there I asked to go in and she said her kids were asleep and didn't want to wake them, but then went down on me right there in the driveway. I asked for her phone number afterward and she gave it to me and told me not to call after 5 since her husband would be home. I asked where he was and she said "asleep upstairs".
Crap like that would happen. I think some might have had a open relationship, but most were just cheating. Like others have mentioned, the percentage of women cheating is almost equal to that of men. Now, I don't think they are using swingers sites to find men to cheat with though. I think it is more like my experience, picking-up guys at clubs, or coworkers, neighbors, etc.
Mr. WS