This is an interesting one.. There is an e-commerce startup, run by a dear friend. One fine day we were chatting around and he mentioned challenges with his business. Challenges included performance, scaling and cost issues about his hosting services provider.
My instant reaction was, why dont you move to aws.. and it clicked just like that.. We decided that we'd start with the free tier, with his mysql server on amazon RDS and rest of app server functionality on the micro instance. All of which is within purview of the free tier. Using Cloudfront we'd localize the static content, to add to the performance of content delivery. Not now, but eventually, we'd start using ELB - the load balancer for distributing load across the instances we would have.
With something like aws, planning all that is really really that straightforward. You just have to be a bit more technically oriented to think in terms of these things and you are set for good.
We are already thinking about configuring autoscaling for the services, so that running on the micro instance doesnt become a bottleneck for the customers. With that we'd hope to achieve dynamic automatic scaling up and down the infrastructure.
We have already taken the first steps, and I am helping his venture migrate to AWS, one of my dream jobs, to be able to consult around migration / integration of Traditional systems to cloud based systems.