I've seen that some interfaces in browsers and in native applications receive a Skitch drag/drop file while others reject it. The native Chrome file upload field works fine, and some custom UI drag-drop zones like what's used in Pivotal Tracker and Jira work fine, but, for instance, Facebook photos does not. Dragging to desktop to create a file and then dragging the file works in all cases. Why is this? Is there something Skitch can do to bridge the gap, or is it something in the programming of the custom file upload widgets that they change and allow for it?