180 degree rule (Amy Z)

This is the 180 degree rule you can see that the camera (blue) only stays on one side of the imaginary line (red) and you have to stick to eathier one of the sides and that side only other wise it would confuse the audience as the character would appear on different sides each time for example the person would appear on the left in one shot and then might appear on the right hand side in the next shot which would look really odd, and confusing so you have to stick to one side.

For example....
http://www.youtube.com/watch?v=QtyrqdK9wi0&NR=1 180 degree rule being broken