Scenario: The customer-facing website must automatically scale and replicate to locations around the world.
Azure ExpressRoute enables you to create private connections between Azure datacenters and infrastructure that's on your premises or in a colocation environment. ExpressRoute connections do not go over the public Internet, and offer more reliability, faster speeds, lower latencies and higher security than typical connections over the Internet. In some cases, using ExpressRoute connections to transfer data between on-premises and Azure can also yield significant cost benefits.
References: http://azure.microsoft.com/en-us/services/expressroute/