My little service dog is vital to my well being.  She has saved me from becoming comatose due to hypoglycemia during the night and alerts me to sudden sugar drops during the day.  She would never attack another person unless she felt I was in danger.  That said, she does growl at other dogs if they come too close, but stays under control and does not attack.

I have been denied entrance into establishments due to the dog, even after saying she is a service animal.  Though not required by law to show any paperwork, I did go online and purchase identification simply to make it easier for people to recognize her status.  However, we still run into problems at some places.

A properly trained service dog is an invaluable asset to its person.  One incident should not be used as justification to deny hundreds of people the quality of life provided by the use of a service dog. 

Again, just to satisfy governmental entities who might question my bringing my dog onto government properties, I do carry a prescription from my doctor indicating the need for the service dog.  I also carry all of her papers from the vet to reassure everyone that she has had her shots, etc.  The Army can request that a service member do the same for his/her service dog.  That should suffice.  Requiring certification from one specific agency is tantamount to issuing a government contract and is in violation of ADA which specifically states that such certification is not necessary and that the animal can be trained by the individual or by an outside trainer.