Not a dumb question at all. Everyone has their way of doing things and it's great to hear ideas about different techniques. That's how we all learn neat little tricks.
I personally always dowel my tiers and place them on cakeboards, even cakes that are only 2 tiers high.
I always keep in mind too that its not just support (although that's the most important) but its also serving. Its very difficult to serve a cake that is four layers high with nothing seperating the layers! Even in 3D or carved cakes I try to seperate every 4-6 inches for support AND cutting purposes.
Very true Kitagrl,
I have made mini tiered cakes, and although I put a straw in there, there is no cardboard between the layers and it can get very messy and not pretty at all.
So, I can only imagine what it may be like in a regular sized tiered cake. Yuck! 
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