I would say that customer service comes into my thinking too. Where's the nearest Dell Store with a Genius Bar which will swap my faulty hardware no questions asked?
If it is under warranty you can return any defective product by mail. I agree that is nice to interact with a real person but at the end when my powerbook broke (out of warranty) the only thing they did was to take it and ship it for repair in the same way any other company would have done.