Over the years I've had my hands on/in every orifice and contacted every body fluid/solid that a dog can create. Rarely with latex gloves in the mouth unless there was something more gross than anything yet described in this thread. I do wash my hands frequently :B I've never had a zoonotic disease.
Unless there is certain behavior like Mark describes, the threat from a lick is minimal and addressed with normal sanitation procedures.
I understand the distaste that some have with licking, me not so much. I much prefer the lick to the bite.
Doug