[venkasub]

Architecting applications for the cloud is a non-trivial problem. Lot of forethought needs to go in place while choosing a particular infrastructure component. And the ideas of resiliency, robustness (what can be bucketed into 'graceful-degradation') etc along with the most important Monitoring needs to be put in place right from the initial days of the app, so that rearchitecting is does NOT end up being a costly affair.

[Johnny555]

Architecting for a physical data center is also a non-trivial problem, and not all that different than architecting for the cloud.

[bluejekyll]

Couldn't agree more. The cloud just makes it clear where you didn't architect for resiliency properly, in your own DC you work around this by doing things that you can't do in the cloud.

But the biggest difference is automation. Because in the cloud you have a full suite of APIs, you can literally automate ever piece of your infrastructure. In your own DC you have to design this stuff to be automated from the ground up, which just making a poor layer2 choice can make that task astronomically more difficult.