I think that if you "want to be transgender", there's a darn good possibility that you actually are transgender. Cis people generally don't want that.
If you're "doing it because your friends are" ... well ... crossdressing is a whole lot of fun. If participating in that CD funtime is the catalyst that prompts you to question your identity, re-evaluate your life, go see a therapist, sort our your feelings, then honestly decide that you are trans ... well ... yeah ... I'd say you were probanly trans all along. A lot of us have our stories about the moment the scales fell from our eyes so to speak. I don't see how that would be any different.
I guess what I'm saying is that I don't believe culture can manufacture new trans people, no matter how "cool" it seems to be.