Sorry to hijack your thread but we have a similar issue. We have a local dog whose owners don't seem bothered about it. It seems a friendly enough dog but it spends most of its time wandering about the streets. One of my neighbours sometimes feeds it as she has a dog of her own.
I checked its collar one day but there were no details on there. I spoke to the council about it as I thought it was very neglectful of the owners, but they said if I didn't know who owned it / where they lived there was nothing they could do?
I only know that it lives in a small cul-de-sac of maybe 6 or 7 houses, but I don't know which of the houses it lives in. Surely just a cursory drive around the area would enable them to pick up the dog, or knocking on 6 house doors couldn't be that difficult? I would not want the owners to know I've reported them, otherwise I'd knock on myself. Some people around our area I wouldn't want to mess with, I have my family to think about.