It's really not relevant at this point, but to reply to both Jonathan and Feppe, the idea of having a bare HyperDrive that accepts USB connected hard drives is quite simple and could be included in the hardware main board easily. However, just as an example, they could make a unit that does not accept hard drives, but only USB 2.5 inch external HDs--one at a time. Now there is no more UI problem than the original unit--it sees all hard drives as ONE drive and copies files like it normally would to each drive. In fact, you can do that right now if you want to remove the hard drive from the unit and plug in another one. So there is no more "controllers" that need to be accounted for. There are several other ways that hardware engineers could accomplish this easy task with little additional cost, if any, such as a switch that shuts the onboard hard drive off when another is detected on the USB port. No one is talking about "chaining" hard drives together--that would be absurd because you only need one at a time for backup purposes.
True enough, having two HyPer Drives is better than one because of the HyD redundancy. But we were talking about cost also. If I had the money I'd hire young female models to accompany my on all my trips and teach them how to download the cards into my 5, 000 dollar laptops. And while were at it, I'll take two 1DSMIIs also, for redundancy. Just joking of course, but it's not just about what is best, but what is affordable.