I don't know if you've read the controversial thread that's going on right now about dry firing, and that's not what this post is about. It's just that I have come up with some questions about the practice of dry firing.

Does anyone here do it for practice?
Is it hard on a gun's firing pin or other mechanisms?
In terms of safety, would loading in a spent cartridge be advisable?
Could the use of a spent cartridge protect the firing pin, etc., from potential damage?
How about loading a spent primer on my inline muzzleloader?