In my life, I have known many people that never set foot in any church, mosque or synagogue except to attend someone else's wedding, christening, or funeral. The people of which I speak have and know the Bible quite intimately. They live the New Testament teachings quite well. They have no formal gatherings with like-minded people, but will often social in small gatherings of the like-minded.
During my mission, I came across two households where the Book of Mormon was likewise used in the home. They explained that three or four generations back, their ancestry had been baptized Mormons into the LDS Church. Since then, none of them, but they knew all of the Book of Mormon names and events.
The house might have a faint smell of coffee or tobacco. When talking with the missionary leader for that ward, we were told in each instance that he (and his predecessors and the bishops) knew about it and it was a 'lost cause'.
As one who believes the title "Mormon" appropriately applies to anyone who believes and follows the teachings in the Book of Mormon (or strongly identifies with the Mormon culture), I refer to these people as Mormons.
I am wondering if anyone is aware of any demographic or sociological data there might be compiled on these Mormons.