http://techblog.netflix.com/2010/12/four-reasons-we-choose-a...
> 3. We’re not very good at predicting customer growth or device engagement.
That really is a large part of why Netflix runs on AWS. Capacity prediction isn't something they can do reliably due to the nature of their service.
That makes sense for a video service.
For 99% of websites, you are not going to have trouble with capacity prediction on the scale of 72 hour turn around for additional capacity. Almost any DC can sell you capacity in under 48 hours and if it takes you longer than 24 hours to deploy...yeah...that is on you.
This is as opposed to a big database driven site like Pintrest that has to custom build pages for every view thousands of times every second. They are far more likely to be memory and CPU bound than Netflix.
That is, AWS has always been a high premium service with the standard story being that you make up for that premium with lower operational costs and more operational sophistication.
But when large (and technically sophisticated) companies like Pinterest and Netflix continue to use it you have to question that story (and to me, especially in Netflix's case as they have the added incentive being a direct competitor to Amazon in their main business).
My current working conspiracy theory is that implicitly or explicitly, the growth of AWS is tied to some sort of regulatory arbitrage and has virtually nothing to do with hardware performance, software resources, or operational sophistication.
That is, AWS allows you to move costs that would have been capital expenditures into other buckets and that is in some way that is obscure to me, very valuable from a business point of view.