Pretty interesting read. Not sure I agree with some of the statements about less system admin and less database folks when they use AWS. I can understand less datacenter staff, but managing virtual or cloud infrastructure is just as much work. Obviously this is only the case when its running customized software and databases built internally (such as netflix). You still need to release software, manage the databases, and handle the same problems you would if you were doing it all in house.
The only items you don't need to worry about would be the following:
Provisioning new hardware (which is pretty simple if you run your own vmware in house)
This is another good read on a website I read. They moved to EC2, and wrote a review 1 year later:
The costs seem to be higher than using a normal colo server, so I'm not sure what the ROI would be for companies moving to EC2 or AWS. It would be good to see some more detailed comparisons of how companies use the services, and what the ROI is.