High Traffic Web Sites
Amazon Web Services makes it possible to design, test, and build an autoscaling application serving network infrastructure in the cloud. It is a matter of a few hours to configure an environment with self scaling database, load balancing web servers, and static content served directly from highly optimized storage.
Add edge serving (serving from distributed datacenters closest to the client) and autoscaling of web/application servers and you have an environment that can handle pretty much anything thrown at it.
We at Ceonex have built and tested such environments. Stress testing using the actual application in ways designed to simuate real usage provides a further measure of trust.