Focus on the entire picture, no. Zoom in on (and then inevitably have to focus), yes. So I guess it depends on the density of capture for me, at least.

I think I can see a big market in that old technology early adopter, the porn market.

People with toddlers? A lot! :)

I think it's only going to be useful after the technology fits into a mobile phone camera.

There's a big disadvantage in having to carry an extra device.

it depends on what you're planning to do with the picture. For example, if you're a designer working with a stock photo, the ability to refocus based on the context where you plan to use the picture could be huge.