I remember that as a kid I had a book published a while ago by Deseret Book that went over all of the various theories and ideas present in Mormon thought about the lost 10 tribes, probably published in the mid 1970s. The North Pole Hollow idea, the space idea, and the Siberian idea all intrigued me. I was unimpressed with the diffusion idea, that the tribes had been scattered among all nations and was unaware of their ancestry. I found it to be very boring and passionless, but it should be noted that this idea is just as old as the crazy ones.

It should also be noted that some of these ideas don't originate in Mormon thought but were already in existence among other 19th Century Christians (not the space idea, I'd bet, but the Hollow Earth idea in particular is not Mormon in origin).