At the Dog Day event, UMN Extension Educator, Bob Mugaas, spoke on lawns and dogs. He provided a great link to an article by Dr. Steven Thompson, DVM, from the Veterinary Teaching Hospital at Purdue University. DOG-ON-IT' LAWN PROBLEMS (Update).
This article is a great resource for Master Gardeners and will help you answer many of the public's questions. Definitely one to print out and keep on-hand.