Was it the Dell model that broke IBM's back?

The more I think about it, the more I'm beginning to believe that Dell is largely responsible for forcing IBM to divest itself of the PC business. This isn't news. Looking back over the course of PC manufacturer history, try to name one buckled PC manufacturer that ultimately didn't crack under the stress of Dell's direct, build-to-order model. The little guys were the first to go and the big guys like IBM and HP have managed to hang on thanks to critical mass and a lot of bundling. For example, it has been almost 15 years since I left IT, but I was an IBM customer and I distinctly remember how my company got discounts on the big iron in exhange for promises to buy a certain amount of the little iron (back then, these were IBM's MicroChannel-based PS/2). That annual quota cut directly into our purchases of the lesser expensive ISA-based PCs from two companies: PCs Limited and Zenith.
Over the coming year, as the general media begins its in-depth chronicling of this defeat for IBM, Michael Dell will no doubt be immortalized as the kid who started a company (and a revolution) in his college dorm room that eventually broke the back of the IBM PC Company. That company, by the way, didn't start off with "Dell" as its name. It was PCs Limited.