They are souls of those trapped in limbo. Once these charlatans sell enough of them they'll bring back the dark lords (and their rings) and the world will be covered with darkness, and raptor jesus shall break-dance on top of it.
Just something you spend your money on, just because you think it's cute and you like it.
It's a viable business. I don't care about them, just like I don't care about paying $5 for a cup of coffee if I like it... it's up to individuals to decide how they spend their money and no one can tell anyone how they can.
If you want to make money out of it, sure, but competitions are high and people earning 1-5 points per adoptable? That's really not worth my time messing around in Paint.
I'm currently giving those a try because I've seen people spend $300+ on them before and I figure if people are willing to blow their money on something so silly I may as well be one of the people they blow their money on.