Feral dogs are becoming more and more of a problem in urban areas. I've heard of roving dog gangs in places like Samoa, or even New York City.
Often no one wants to bother with going through the process of locking them up, or destroying the dogs. They get used to attacking small animals for food, and eventually get too bold around humans as well, which is when they stop being cute.
I think it all comes down to people being made to neuter and spay their dogs, so they don't end up dumping puppies which can become feral. But, unfortunately, people don't seem to be willing to take that responsibility.