[majewsky]

I'm not familiar with how S3 works in detail, but I imagine this could require additional API calls in the backend which increases the latency and resource usage of API requests. In the worst case, such a change could easily require Amazon to purchase dozens, if not hundreds of additional servers.

[acranox]

With the rate of AWS growth, they probably bought dozens more servers in the time it took you to write out your response. :)

[majewsky]

Likely, but Amazon didn't get where they are by ignoring small costs.