We just got back from a trip two weeks ago and dogs in general are on the rise in the theme parks. Most of them wore some sort of identification as guide/therapy/medical assistance dogs, but there were some that didn't.
I really wish that WDW would make working dogs wear some sort of identification, be it harness, tag, leash with medical symbols, or something like that. I've been working at teaching my 3 year old never to bother working dogs and never ask to pet or interact with any sort of medical guide dog because they have important jobs to do. Its tough when the dogs don't wear anything distinguishing, because then they just look like the pets at the park and its confusing for kids.
As a side note, in the airport I saw a medical dog of some sort that was wearing a harness, but then the harness had a patch that said "ask to pet me, I'm friendly". I thought that was crazy, talk about sending mixed messages!