Im pretty sure it has to boot from SD card for it to work. I believe I read that somewhere, but I could be wrong.
The GPU firmware, kernel and initrd have to be loaded off a SD card but I don"t think anything else has to be.
That would make sense. But if the OS isn"t on the SD card then how will you be able to delegate which boots first with no BIOS?
With a boot loader of some kind on the SD card. After the blob is loaded from the SD just tell it to load the remaining files off a different drive. It is true that there is no getting around having an SD card but only a couple files actually have to be on it, this has been discussed to death if you run a search. Many of the lucky with Alpha and Beta boards have reported far better performance running off of USB sticks or USB HDDs than the SD card. I'm sure there wil be tutorials shortly explaining or showing how this is done. But it has already been done, so I know it is possible.