Thank you, Mark! Well, it depends on the perspective. Plovdiv is good for businesses because of the flat 10% corporate tax and the cheap labor. On the other hand, it's not so good for most of the people that live there because the average salary after tax is about €400-450. And although Bulgaria is cheap, it's not cheap enough to be able to live comfortably with €450.
And as the rest of the region is much worse economically, people have no choice but to move to Plovdiv. Sometimes with their families.
I guess that you can find such wonky-angled streets in most Spanish cities? :)