In Bed with Strangers

The term "swinging" calls to mind a bygone era of 1970s sexual liberation--images of shag carpet, hot tubs and married couples swapping motel keys. The Internet age has made swinging widely accessible and discreet to a broad range of participants, married or single, and of any sexual orientation.

Some people pursue the excitement of spontaneous, noncommittal sex with strangers, while others s...