I expected this to be about how many Mormons one runs into these days don't really seem to be serious about their religious beliefs, but are instead just going along for the social benefits of belonging to a community that in some ways seems to work. (I.e. how many Mormons actually seem to be pretty similar to typical secularized somewhat-sensible-and-moderate Christians, despite stereotypes of them being more serious regarding their religion.)
The Society for Creative Anachronism started as a backyard graduation party for a medieval studies student and grew to 32,000 members as of 2008. Does anyone have any insight into how that happened? Of particular interest would be any intersection between the SCA's mode of growth and the usual modes of growth of religions (keeping in mind that not every intersection would be worth incorporating into a strategy for raising the sanity waterline by spreading LW-style ideas and approaches).