You can certainly get mold when hanging if your humidity is too high and you have no air circulation.
I assume plants are hung in general to keep air moving around the drying plants, which is maybe what the previous posted was getting at. With air moving, you'll avoid mold and speed up the drying process.
i find when i leave smaller stuff, although it takes 2 or 3 days longer to dry, it tastes 10 times better.
i think the smaller foliage kinda cures it while it dries a bit.
which is good for me, becuase my stuff doesnt last long in jars.