I agree with most here that dropping the bean bag when you don't really need to isn't an issue. However, I've recently seen a few officials (mostly veterans, and veteran white hats at that) who seem to have lost the plot as to why -- they just react "fumble = bean bag" and make no attempt to actually marking the spot of the fumble. A play a saw a few times on a recent rainy JV night -- run up the middle, 3 or 4 yard gain, gets hit, wet ball slips out of his hands... white hat, who is now 10 yards behind the ball, see the loose ball and drops his bean bag at his own feet nowhere near the spot of the fumble.
Ultimately, we are trying to mark a spot with the bean bag even if it's unnecessary to do so. It shouldn't just be a "Hey I saw a loose ball" signal. I can be both.