The cloud promises unlimited capacity, pennies per hour to operate, 4+ nines of uptime and infrastructure managed by a dedicated staff. Even technical challenges around security and compliance can be achieved and are no longer suspect. So why wouldn't you send everything to the cloud?
Originally used as an inexpensive alternative to quickly deploy services outside the realm of IT, cloud computing is quickly becoming a de facto standard for new application resources. The challenge is how to manage those resources transparently. The cloud should be an extension of the internal data center, and cloud bridges, gateways and brokers are all components that IT should focus on for connecting to their external cloud deployment.