I've noticed a lot of articles from Mormon publications and otherwise reporting on the popularity of the site among the Mormon population. Is there a particular reason why?
Without access to any proprietary statistics, according to Quantcast, pinterest is significantly popular with women who are into parenting, home/family, hobbies & collectibles, bridal, home decor, toys, kids, foods, baby, etc.
All of the above is pretty significantly the stereotype of the Mormon housewife. :)
Colin Jensen got it right. The only thing I would add is that one look at the "mommy blogger" trend in the blogosphere and you'll find your answer: some of the most popular blogs happen to be Mormon women that generally write a lot about fashion, family, food, etc. LDS people tend to be fairly tech-savvy, and Pinterest just happens to be a good platform for sharing content, which LDS people (women, in particular) do a lot of via blogs, facebook, etc.