I'll agree with you on that. I saw a few things that looked way too young!!! I thought they were gonna croak at any time!
I had two two week corns at our table, but they were for display and NFS (they're my keepers anyway).
I'm not sure if there's a certain age or in the case of snake a minimum amount of meals an animal should have to be sold, but I think that's at the discretion of the seller, and as a buyer, you should always ask questions about age and "establishment" of the animal. Myself, I never buy under four weeks for a lizard and don't consider a snake established until at least 2 - 3 meals.