Just a mild +1 on the "social" aspect... we have a very large crop of newbie W4's this year, almost all of whom are part of a handful of new-ish clubs that are women-focused, are recruiting effectively using women to recruit women from tri's and runners... to me this is a big change from the past / usual "wives daughters girlfriends" demographic that brought newbie ladies to races.
Time will tell how many get the bug and stick with it, but washout rate is high among men also.