I tend to separate out infrastructures into two different beasts: A site, and a super-site. Super-sites get tremendous amounts of traffic (1 Gigabit+) and typically are associated with a brand, such as Amazon.com, Google.com, or what have you.
On Slashdot today was a posting about the infrastructure for the super-site Wikipedia. And what load balancer do they use? Why, Linux Virtual Server of course.
