WHEN A COUPLE performed a sexual act in front of a University of Pennsylvania dorm window earlier this year, at least two cameras clicked away. The couple's faces are not identifiable. Only a pair of buttocks, a pair of legs and a bare back can be seen from the window. The gender is unclear. Yet the grainy photos have touched off a controversy that has roiled the Ivy League campus and once again has plunged Penn into a rip-roaring controversy over free speech and student rights. One of the photographers, an unidentified Penn junior engineering student, is facing sexual harassment...