Allow the user to specify a delay for Dropbox to identify a file for syncing, and check if the file has been deleted during the sync.
Some applications create temporary files/folders beyond the control of the user. If these files are held open by Dropbox when the application attempts to remove them, they are left behind. Of particular issue are applications that generate HTML output files. A temporary directory can be left behind that if deleted by the user, Windows will also delete the 'linked' html file. This causes endless headaches.
The delay should be user-adjustable with a default of 0.