> Preview images of what? Images usually should be routed through a CDN which caches them directly in the user's country. It's extremely cheap and easy to set up. Nothing compared to running an application in multiple datacenters.

I don't think most service cache data that isn't normally used in that region. In my experience I noticed that Twitter, YouTube, and Facebook feel sluggish when you are viewing Japanese content from Singapore compared to viewing the same content in Japan, etc.