Public confusion, legal loopholes and shady Internet businesses have led to an "epidemic" of fake service-dog certificates, vests and harnesses for use on ordinary pets. And advocates for the disabled say the issue is creating big headaches for those who truly need the canines' assistance. The problem has gotten so bad that Canine Companions for Independence — the nation's largest breeding and training service-dog program — launched an online petition this week asking the U.S. Department of Justice to take action. "Unfortunately, people are trading on the fact these harnesses and vests have become distinguishing marks of service dogs, so...