Sure you can buy some extra capacity to be able to scale, but only to a point. With ec2 you can "instantly" scale 1000x if you need (and built for it). You don'

Sure you can buy some extra capacity to be able to scale, but only to a point. With ec2 you can "instantly" scale 1000x if you need (and built for it). You don't afford to have 1000x dedicated boxes idling in case you need to scale. BUT! If you have a consistent load or are "big" if may very well be cheaper to build your own infrastructure with dedi/colo and later your own DC. Ec2 is good in the beginning when you truly need to be elastic and of course you will pay for that feature. But a lot of the players out there uses both their own stuff AND cloud.