I thought you might have meant that. Iwata didn't specifically say that they're not tied to the console. When I read what he said, it seemed more like Windows-style account switching.
Guesses on how big the HDD will be in the Wii U?
I was thinking about this last night and I would hope it's 250g, but I could see them putting in a HDD that's less than 100g.
None. Just 8GB of flash, but you can use any USB HDD.
Also, a <100GB HDD would actually be more expensive than a 250GB due to nobody making them anymore.