Looks like a great service. But where do images get uploaded to? I currently run a site called Desktop.ly where users can upload a picture of their desktop. When uploaded Imagemagick is used to convert the image into different versions using the Carrierwave gem (Desktop.ly is built using the brilliant Ruby on Rails!).
How does Filepicker.io work like this, where are images stores, can this be a custom Amazon S3 or Rackspace Cloud Files storage? Can images be resized? Does/will it work with RoR to offer a seamless integration?
Plus, what happens with downtime? Of course this will be a big thing with many web services.
Hope you're able to answer my questions. Also, check out Desktop.ly ;)