Simply pushing a VM into the cloud only solves part of the problem. Throwing more CPU, memory or IO resources at an application only goes so far, as we've seen with applications such as Exchange 2003.
What's needed is to ultimately re-architect applications in order to better leverage the cloud. I think one implication of this analysis, though, is that architects can expect their underlying networks to be stressed as processes are distributed between the cloud and enterprise networks.
Application components resident within the enterprise will need effective connectivity with the components resident in the cloud. The security and management implications are enormous, as are the networking performance issues. Great attention will have to be paid to the interface between the cloud perimeter and the enterprise data center if organizations are going to leverage the hybrid cloud.
This point was alluded to in the recent release of Gartner's Magic Quadrant for WAN Optimization Controllers (WOCS), where data center-to-data center connectivity is seen as an emerging role for products that have traditionally focused on accelerating data center-to-branch office links. But leveraging the cloud is only one application that will drive the increased use of WAN optimizers within data centers.