packrat
As far as I know, every hard drive made in this century ships its heads automatically when power is removed, and most do so after x minutes of inactivity even when power is on. You'd have to hit it with a big hammer to do any damage, though if it landed really badly, you could break the circuit board. I'd worry more about static electricity.
I've got about 20TB of data, accumulated over the years, and hard drives are the cheapest, highest density, and most reliable solution for archiving. Some of my drives date back fifteen years, and I've never lost any data from any of them. I checksum everything, looking for changes, but I haven't found any. As long as you store them vertically and run checks on them every few months, they'll keep going. I keep them in conductive bags, in cardboard drive storage boxes.
I'd love it if someone would start making really high density (TB) optical discs, but the movie people would never allow it unless it was hideously crippled so they could pretend that it couldn't copy their blurays. I guess if m-discs really store 100GB, I could burn 400 of them (got to have at least one backup) and theoretically store them in roughly the same space as my hard drives, if they were in cake boxes, not regular cases. 🙂