> many apartment dwellers already live in tiny spaces.

True that. People in Hongkong or Japan are already living in teeny tiny house/apartments. And some go to extreme lengths to maximise their space. (http://www.youtube.com/watch?v=Lg9qnWg9kak - Apartment with movable modules in Hongkong )

Indeed, this article is very focused on North America with its huge houses. Then again, I do expect houses to become even smaller in the future, in any country. After all, there will be more people in the same space.

Even further into the future, people might spend their entire days in virtual environments so 'real space' will start to matter less.