Drag and drop handling depends on understanding the interaction of each version of each browser and each operating system that host them.
We've shown that we can do some and that it is a reasonable way to connect neighborhoods within the federation. We need drag and drop.
Federation
Dragging a federated wiki url to another federated wiki (outside of a factory) should add additional pages as if they were opened following references.
Internet
Dragging an otherwise undistinguished web page to a factory should write a paragraph that summarizes the page, possibly relying on header content, possibly reading for useful html5 tags.
A factory created citation should use the Incremental Paragraphs convention of appending one-word links to the end of the paragraph. Use website, webpage, blog, post, github, pdf, or other recognizable indicators.
It could be possible to link-check pages created this way. A fingerprint of the cited content could be checked when the item is viewed while logged-in.
Resources
Like Gmail 
especially relating to dropping multiple files.