Infinite minecarts can be placed in one location; many TNT minecarts make weird craters

By right-clicking the side of the collision box of a rail, it is possible to place an infinite number of minecarts on that one rail. If this is done with TNT minecarts, it is possible to make many TNT minecarts detonate at the same time and place, which creates a very strange crater, and can launch things very far away.
Example video here.
(This video also demonstrates [MC-6594].)