I, too, would like to bury them in my own backyard. However, we move around alot, and I hate to think of them being being in a stranger's yard, and that would also nix the pet cemetary as I probably wouldn't be back in the area to visit.
I have though alot about this, as Keiko is getting older. Mind you, she's only middle aged, but you never know what might happen. I have a couple of options. 1) cremate and keep the ashes to display or bury when we do have a permanent address. 2) bury them on my parent's property. 3) get her stuffed....... ...just kidding. My mom used to joke she was going to stuff their cat and place him on the couch when he passed.
I have buried hampsters in the backyard before. My parent's no longer live at that address, and I have to smile thinking if anyone dug in either garden on the property they would find numerous corpses.