@mpjgregoire That's the exception that proves the rule.
I'm sure a lot of Toronto (think the parts with gridded streets) is much less concentrated than the parts where suburban malls are. Have you noticed that, outside the insane lack of prioritization of streetcars over private automobiles, the former parts of Toronto are quite livable? Think of all the 2-or-3-over-1 rental/retail that lines so much of every major street. So many mom and pop shops compared with any suburban mall.
@virtuous_sloth Maybe downtown Toronto is the wrong place to test your claim that ownership of commercial real estate has become more concentrated over the last hundred years. Not sure what the right comparison would be...
Mixed commercial/residential buildings are obviously a good idea, and so it's hard to believe governments ever passed laws to forbid it. Euclidean zoning was a terrible idea.