Looking at the iQ and how it may look when it debuts, I wonder if it would be worthwhile to lower the vehicle at all. Would the benefits from lowering the car outweigh the other negative factors that may arise with lowering a small car?
You will see more wear and tear on some components. It depends what options are available to lower the Scion, if any after market. A good set of coilovers and a camber kit and you should have no real worries.
I would not lower that car. Its already fairly low for its a car thats not a sports car. However if you do lower it at least do it properly so that you can avoid having problems with day to day driving.