I think some people would be shocked to actually know how many sl females they have interacted with are males real life.
As far as real life men playing female avatars convincing people in game and on forums they are also females in real life, have fun lol. That's a big part of that game eh!
It's actually an art form and subtle on so many levels. For example, you would never directly tell some one you are female real life. You use heuristics, which is basically inserting clues in casual conversations so that they decide you are a real life female. . For example, you meet a female shopping while impersonating a female. You are talking about the clothes and you say something like, "omg if my real life boyfriend knew I was spending this much in a game on virtual clothes he would kill me! lol "