Suspending from your chest would not work since the length of the tank would place the bottom below your groin, making it difficult to kick. Also, many divers (myself included) clip other diving necesities to the front of our BC's. So if the tank was there, where would we put our goodies?
Plus, I have seen tanks slip out of their bands duing a giant stride entry off of the boat. If the tank was in front of you and do this, it would at least knock your regulator out of your mouth and at worst break your jaw.
Placing it on your back is not unlike placing your book bag on your back. It's out of you way, and you can "forget" about it during your dive.
BTW, I like your Ace Ventura impression.
[This message has been edited by TexasMike (edited 07-07-2001).]