Worst experience as a dog owner?
Mine was when I got harassed for having dogs, because they only want to kill little childs and are humans worst enemy. They even tried to throw rocks on my dogs. Luckily the police was there quickly. I guess they were pretty drunk.
The seconde one I guess was when a mother (a stranger) didn't stop her children from trying to pet and feed my dogs, because they are so cute and a little petting won't harm them. Sadly I know many other owners who experienced something like that.