I think it depends on the dog and the situation.

I see dogs outside without their owners and it makes me sad. Every day on the way to school and on the way back from school I see the cutest little BC pup outside all alone and it makes me sad. I have to wonder what kind of situation would make it alright for a puppy to be left outside all day. Judging from the lack of stimulation in his environment and the breed (and the herding characterstics are written all over this pup!), I'd say that the owner never did the research and when the pup is indoors he's nipping people's heels and chewing on everything. So they leave him outside in rain, snow, or hail (I've seen him in all).

Then again, I also know people whose dogs just don't like to be indoors. My aunt's RB Australian shepherd didn't like the indoors. She liked to lay out in the shade. Plus the indoors was a scary place for her -- she was old and had gone deaf, and the children would often pop out of places and scare her unintentionally. She liked to bury her biscuits in the dirt, and had a hard time doing that indoors.

So I think it is fine as long as the dog gets lots of love and attention and actually enjoys being outside. If the dog is lonely and sad and feels seperated from the family, I just don't think it's right.