1. A method of using dynamic capacity-on-demand techniques for re-routing traffic in a distributed computing network, comprising steps of: comparing current workload conditions, at a system which receives a content request, to one or more threshold values to determine a current operational mode of the receiving system; and serving a modified version of the requested content, or an unmodified version of the requested content, depending on the current operational 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.