This may be a better discussion for the water cooler but, I thought this crowd would be best to check with first.
Walking into the office I pass a maintenance closet everyday that houses grounds keeping equipment for the crews that take care of our building a parking garage. This morning I happen to spot keys hanging from the door knob. 
I moonlight as a volunteer fire fighter and first responder so my first instinct was to make sure there was no one in the closet overcome by chemical fumes or suffering some sort of cardiac event. After knocking then opening the unlocked door I verified there was no one in the closet so my day job kicked back in. I immediately thought about the level of physical access these keys grant to my office and how this was a possible risk to my company as well as others in the building.
Fortunately, one of the crew I'd seen before came up the closet and I mentioned finding the keys which he laughed off.
I have no interest in tattling on the maintenance crew for creating a risk. I'm hoping the guys realized there was a problem with the situation especially given the open access to this closet in a dense downtown area.
So the question is: Do we have the responsibility to report security risks like this? As of right now, I plan on letting it go and keeping an eye out for future occurrences but I'm concerned that is just the amount of complacency that gets us into trouble.