Didn't they mention using barcodes at first, then moving on to another method later?
What I extrapolated from what they said in the briefing was,
-the eShop will have a "barcode scan" button added, so you purchase something and be presented with a barcode.
-you scan in the code on your 3DS and it starts downloading, you will also be able to close your 3DS before it's finished and it will continue downloading.
Exciting when they said it would be useful for "large downloads". Full retail games? Massive Shop games?
Can't wait to find out.