Okay, so you understand webfarms now. What's the magic that actually distributes the load, and how does it determine how the distribution is handled?

Networks can be configured to be so incredibly redundant now - for reasonable
prices - that there is no excuse for a data center not to achieve five nines
(99.999%) of availability. But what about the servers and applications? Why spend so much time up front
configuring the network to make sure it doesn't fail, and then deploy an
application to a single server?