"...wouldn't movement out in the field be likely to damage the hard drive in the MR-1..."
The small hard drives used in music players are pretty durable. There are millions of iPods and other music players in use with small hard drives, and they rarely experience disc failure. Of course you need to take some precautions. Don't drop the recorder, and stay away from the mosh pit if you're recording. Don't set the recorder on a surface that vibrates with the music (or the dancing).
The MR-1's one-bit recording produces a prodigious data stream. The 20GB drive in the MR-1 is sufficient to hold only about 7 hours of one-bit 2.88mHz recordings. That's why a 4GB Compactflash card wouldn't work well as storage for a one-bit recorder.
Flash memory has three main advantages over a hard disc. Flash memory is more durable, faster, and uses less electric power than a hard disc does. Hard disc is cheaper per MB, and available in capacities larger than flash memory offers today.
I saw a name-brand 16GB Compactflash card for about $105 after rebates from a reputable dealer this weekend. As flash memory gets cheaper and available in larger capacities, I expect manufacturers of field recorders that use hard discs (e.g., Korg, Edirol R4) to switch over to flash memory for storage. Future iPods and even laptops will switch to flash memory, too.
Flintstone