Flying a Cherokee180 I will always turn off the the engine for safety
sake and I won't start the engine if there's someone behind me,
fueling or working on their airplane. I will turn the plane away from
that individual for safety and out of courtesy. There's no reason to
take a chance. I use the chocks everytime I leave the airplane,
including in the hanger, and carry several sets with me. The larger
airports with a lineman will usually use their own set of chokes. I
have helped push a Cessna out of the snow with the power applied and
the slip stream was pretty strong, not something I would wish on
someone else.