I've watched this video 3 times since you posted the link here. Something about is really bothered me right off but I couldn't really say what it was. Maybe I'm just slow on the uptake but I've figured out why this seemed bad to me. Don't get me wrong, it's a powerful tool and really cool that it can be done. But, and there's always a but...
It really makes the image and the composition seem unimportant, like an after though. As if the picture or photo itself was only icing on a cake, the cake is the important part, what's on the cake is secondary.
Who cares if someone takes a really nice photo of a landscape, you can revise that landscape anyway you want :P
Again, it does seem useful and I'd probably wouldn't be against using it in some places. But it does make my heart sink thinking of how little value is placed on the image as art :P
Someday maybe the whole world will be resizable...
Maybe I was a Luddite in a past life?