The not burying thing was from my vet in Arizona - any euthanized animal has to be cremated or placed in a "proper" area such as the city dump...
this was in a rural area where there's lots of critters that might dig up a dead animal to eat. I'm pretty sure this is local law, but I'd have to look it up, I know the vet was adamant about me not burying the dog if she were euthanized.
I lived in a residential area, that's why I took our dog out to my grandparents ranch - and we weren't allowed to bury anything in our yard on the military base - they have the same rule here that if your pet passes away you have to contact the base veterinarian and have it properly disposed of.
Some places it is illegal to euthanize animals by shooting them and they have laws/ordinances against it, I read something about it not too long ago, I'll see if I can find the place.
http://www.ens-newswire.com/ens/oct2002/2002-10-10-06.asp
Found a link that talks about euthanized animals and their burial - consequences to local wildlife, etc.
In 1999, a veterinarian from northern New Mexico euthanized two mules owned by a rancher in Colorado, leaving the carcasses on the rancher's land. Five golden eagles and two bald eagles died after feeding on the carcasses. The rancher and vet were fined $10,000 each for violations of the federal Endangered Species Act that resulted from the improper disposal of the mule carcasses.