I can't even imagine how you'd bread a chef's knife back near the handle! I don't baton firewood with my knives, I just use 'em on food!

Nothing I do puts that kind of stress on the blade, as as far as I'm concerned if you do use that much force you're asking for trouble. In almost every case where I've seen a knife break it was at the tip, and occasionally at the heel. Tips will break if the knife falls point first, and I've seen people break the heel using their knife as a can opener. In the latter case a nice bolster may have saved the heel, but since a knife isn't made to open cans I don't really consider that a benefit. A coworker I used to work with did snap the blade off my Messermeister tourne knife right at the handle a few year ago. Claims he was just peeling an onion and it snapped. Hmmm...
I've placed dial calipers on a lot of knife spines. Some of the very thinnest I've ever seen are the stamped blades of the Forschner Fibrox knives. But thickness of the spine doesn't really tell the true story; how well a knife cuts is more determined by the bevel angle and the thickness of the blade behind the edge of
Damascus Steel Knives. Although a truly thick spine can cause a knife to wedge, I've found cutting performance more affected by thinness of grind more than thinness of spine.