1. A method of using dynamic capacity-on-demand techniques for re-routing traffic in a distributed computing network, comprising: comparing current workload conditions, at a system which receives a content request to determine which of a nominal mode, an intermediate mode, and a peak mode, the receiving system is operating within; serving an unmodified version of the requested content while in the nominal mode; generating a modified version of at least a portion of requested content while in the intermediate mode; continue serving an unmodified version of the requested content while in the intermediate mode; and serving the modified version while in the peak mode; wherein: the modified version is programmatically created from the unmodified version by rewriting selected ones of one or more embedded content references within the unmodified version; and the rewritten content references refer to resources which are external to an enterprise in which the receiving system is located, such that subsequent requests for each of the embedded content references are automatically directed to the external resources; and the embedded content references in the unmodified version refer to local resources of the enterprise, such that subsequent requests for each of the embedded content references are automatically directed to the local resources.