When you see a bunch of dogs happily playing freely in a fenced-in dog park, are you able to spot their owners? Science says that it's possible, especially if your dog is a purebred animal. The theory that dogs look like their owners suggests that people simply choose dogs that look like they do, which seems a little vain but probably true.
Then again, it could all be in the sale: salespeople tend to pitch items to their customers that they think looks like said customers, with a common example being the tendancy to push rounder cars on rounder people. It's not a very pleasant practice, nor a very nice one, but if that's happening to cars, maybe it's working with dogs, too. Then again, people are often given time to play with new dogs or adopt from their own agency of choice, so it does seem less likely to be the cause of people actually looking like their canine companions.
Does your dog look like you? Do you think people tend to look like their dogs--or their cats, for that matter?