There's a great conversation going on about why social networks, specifically Google+, shouldn't require that all its users register using their "real" names. To catch up, read Skud, Caterina, and Anil. I've got nothing to add to their points, except a quick personal story.
I was 16 years old when I knew for sure that I'd never have a boyfriend or a husband, that I was in love with a girl. At the time, I was a student at an all-girls Catholic high school, wearing a plaid skirt and dodging the nuns in the hallway. It was awful. I spent most days totally stressed someone would find me out. When I arrived at college, I promptly cut my hair, put on freedom rings, and looked up the gay/lesbian/trans student group. There wasn't one. After I spent my freshman year befriending all the gays on campus, I set out to start one.
But there was a problem. My school had a policy about establishing student groups: you had to have a certain number of members, that is, a list of student names and IDs to submit to the administration to establish interest and get a group charter (and thus funding). Of all my queer friends, about three of us were out of the closet and willing to put our names down on that list. (Seriously, conversations about establishing the group went like this: "How will we advertise meetings? We can't put the room and time on flyers, because the football team might show up." It was a dark, pre-Glee era.)
In the end, we "hacked the system" and got sympathetic straight students to sign the list for us, and the GLBT group charter was granted. Without them, that would have never happened.