I've known about this for awhile.
I wanted one, so I looked into it. The so called Mini Pigs are just starved pot belly pigs. One "breeders" page that I looked at actually included the dietary restrictions in their contract so you couldn't return the pig if you actually fed it.
It's actually a really horrible situation. Pigs can be really fun animals and I've been around house pigs (pot bellies) that were really awesome, but it's not something everyone can do and it's not like having a dog.