In reply to girlymonkey:
Yeah, as Chris says. In front wheel steering, the front moves round the corner and pulls the back with it, resulting in a tighter turn at the back end. (If you look at tyre marks, you may have noticed the marks of the rear wheels are tighter in)
If you steer from the rear wheels, you have to move the back end to make the front point in the right direction. Try it with a remote control, pretend one end is front and the other is the back, and move it along the edge of a table to the corner. Now, to make it move around the corner, you would have to swing the back right out so that the front stays on the edge.
This is essentially the same as rear wheel steering, as you can imagine if you happen to be overtaking it when it goes around a corner (like a cyclist would) you might end up rather perturbed!!