More years ago than I care to think about, my best friend (we'll call him Sam) and I were as close as brothers. We'd known each other since we were 8, and spent every single weekend either playing at one of our homes, or at the park/beach/woods. In our later teens, without any experience (both serious nerds, so not attractive enough to the girls we knew), we were extremely curious about sex. One weekend, his parents were...