This. I've had to have an animal euthanized that was bought from a vendor that I later found out was really an animal flipper. The well-known vendors will often give you their card or a number to contact them if you start having signs of illness or parasites with an animal they sold you and offer some kind of guarantee/help/etc. But there's a lot of vendors that will operate under caveat emptor ("buyer beware"), and they're done with you as soon as you hand over the money.
There's still plenty of great deals, vendors and people at the shows... just really have to know what you're buying and who you're dealing with. Small bright side, the regulars and bigger breeders will often tell you who do deal business with and who do avoid because of whatever reason.