Kind of like a drunk guy that is toying around with his "unloaded" gun at a party. Probably nothing going to happen. It's probably unloaded like he says.
But man, it makes you uncomfortable, because you have no way to know if it is, and you don't trust his ass, and you sure as hell don't want it pointed at you in case he pulls the trigger like a stupid.
Backhoe is probably safe 99/100 times... but you're really trusting the people who maintain it, and the guy who parked it, and you don't play Russian Roulette even if the revolver has a 100 round cylinder. There's more things that can happen that just equipment failure. (ground instability, earthquake, etc.)