There is only one logical explanation: Lee Harvey Oswald did it!  Really, the demolition theory is at the core of the conspiracy buffs argument (that and our goverment flew the planes etc.). If there was a legitimate chance that a controlled demolition was needed to prevent the whole city from toppling like dominos then this should have been ...

Mass transit makes sense if you have enough population density.  When and as cities grow (some do), congestion reaches a point to where the benefits of having independent transportation is less than the benefit of mass transportation.  There are only a few places where this is an issue and China will or is projected to be faced with most ...