Amazon.com is a great company and a early innovator in the Web Services Community. (God knows I send them ALOT of money.)
So this is not an indictment of Amazon as a technology provider. In fact, it is because a Amazon is a great company with a solid infrastructure that this is significant.
As Geeks, we tend to get all jazzed about the latest buzz - and cloud computing is certainly one of them. But, I think it's important to remember, while services in the cloud can be very cost effective. You can't control the cloud.
When you build it and own it you always have options when you're not getting the service level you need. In the cloud, you're held hostage by 3rd party service levels.... ad as we all know, stuff happens.
When you're using a cloud hosted service, remember to build support for graceful degradation your application. You application need not fail completely because you can't fetch images, ads, etc.
Not only is this good design practice, but it mitigates a DOS security threat. If I wanna bring your web application down and you haven't built resilience into your site, all I need to to is successfully attack any one service your application depends on and your application is down !!