Here is an interesting article about dogs in shelters- Buy and return: improving outcomes for animal shelter dogs. It reviews some of the most recent studies relating to why dogs wind up in shelters, in many cases, multiple times.
Quote from the article :
While only 30% of animals relinquished to shelters are reported as having
behaviour problems, the majority (69%) of people who acquire dogs from shelters
report their dog as exhibiting behaviour problems (Wells and Hepper, 2000). Of
these problems, fearfulness, excessive activity, destructiveness and
inappropriate elimination were the most commonly reported problems. Of animals
re-relinquished to the shelters studied, over 90% had exhibited problem
behaviours as compared to 67% of those which were kept by their owners.
Ms. X wrote once before that what is really needed is free training classes for dogs and owners. If any of my furry readers know of free classes in their area, please post about them in the comments.