A Microsoft file hosting and synchronization service.
The sad truth is microsoft would rather try to coerce you to buy more storage space than allow you to empty the Recycle Bin. You have to go through the "Manage Storage" button, dismiss the popup selling more storage, and click on the blue link that say "Empty Recycle Bin", listed on the "Manage Storage" page. When the action confirmation popup box comes up, it confirms what I allege because it clearly states, "Are you sure you want to permanently delete the contents of the Recycle Bin to create more space?". Almost as bad as apple.