The classic American shopping cart has two wheels at the back that are fixed in a forward facing position and two wheels at the front that turn in the direction that they are pushed. For some reason, one of the four wheels always seems to have something stuck in it so that it doesn't turn well, or it swivels from side to side incessantly as you push the cart around the store. In contrast, the standard Australian trolley (as shopping carts are known to Australians) has four wheels that swivel and rarely seem to insist on a particular direction.
This post has moved. Read the entire post at http://wombats-and-cents.blogspot.com/2007/06/beware-australian-trolley.html