With recent news regarding Revolution's "Virtual Console" people have began to question what storage method the console will support. We're already aware that SD cards will be supported, its a very affordable solution and provides pretty good capacity.
In an interview with CNNMoney.com, Satoru Iwata, the Nintendo President was questioned, but of course replied with the usual answer; we'll find out at E3. However he did offer some insight.
"The Revolution has 512 MB of flash memory, allowing for some initial storage space. The system also has a slot for SD memory cards, which are widely used in digital cameras and can hold a greater amount of data. Most importantly, Iwata mentioned, were the USB ports that are built into the Revolution "so practically any storage method can be used".
Which would certainly explain the reason behind USB ports. We'd already questioned their presents after being shown at GDC last week. SD Cards are also a very realistic answer for most gamers, buy a 2GB card for roughly the price of a game, and you've got yourself 2.5gb in total. That's more than enough space for a huge amount of Virtual Console roms, even the larger N64 titles only weigh in at around 32mb.
If the Revolution supports standard USB2 external hard drives, they're onto a winner for the end user. There might however be slight piracy concerns over supporting 3rd party hardware via the USB ports.