After many conversations with the owner of a big chow, I finally put a hot wire around my front flower bed - of course, I had to turn it off when my doggies were in the front, but the neighbor's dog found himself another potty.
In the same neighborhood, an upscale, gated, private lake, a man would walk his bichon into my yard to poop because it had "shady oak trees for him to stand under". RUDE! RUDE! RUDE!
(not to hijack your thread, but it also ticks me off when people have a bunch of cats that crap in my flower beds.)