[D]og owners are some of the only regularly walking people in a community -- many neighborhoods outside of the inner core of Washington are dominated by automobiles and there is relatively little positive pedestrian activity on often empty sidewalks.
Dog walkers contribute positive activity not just to streets and sidewalks but to parks. It's very easy for a park to devolve into a dangerous place. One technique for people committed to disorder to keep people (especially families and children generally) out of parks is to break a lot of bottles -- broken glass keeps a park free of children, making it easier to conduct illicit business and activities.
The piece reminds me of Jane Jacobs' argument about the value of "public characters"-- or as they were called on Sesame Street, the people that you meet when you're walking down the street each day.
Should we also think of dogs (or other animals) as public characters as well? Are there certain kinds of animal ownership that you see more of in well-functioning neighborhoods?