Fess up - which bands or musicians have you been that obsessed with that you actually went as far as to join a club or write some fan mail? OK, I'll start. I'll precede the confession by saying that this was a VERY, VERY long time ago...and is of course no indication of my excellent current music tastes...
I once wrote to the John Travolta fan club. There you go, I've said it. (and was super excited to get a response).
Joining Keane's fan club in my 30's seems like nothing compared to that :-)