Many people just throw a lamp... wherever. And who cares right?
As long as it's giving off light it doesn't really matter. Well, it does.
The placement and type of lighting in your home can help save energy. For example, if you place a lamp in the corner of a room instead of on a flat wall the light will reflect off of two walls instead of just one, so that you only have to have one lamp instead of two. And if you choose lighter colored lamp shades the light will come through easier and that way you can save energy.