Dropbox Rogue FAQ question and answers in the table of contents, or buy the book here.
How do I delete Dropbox?
Deleting Dropbox can be as hard as killing a vampire. You may think normal methods are enough to do the job. But just when you think you’re done, it pops up alive and kicking in some other place.
You can easily delete the Dropbox application from your computer, just as you would any other application. But the Dropbox folders still remain on your hard drive. To get rid of those folders and the files in them, drag and drop them to your trash on your desktop. Note that this will not completely erase the data from your hard drive. To do that, you will need to use a special utility -- Google “permanently delete files” to learn more.
In addition, even if you have deleted the Dropbox application and folders from your computer, the data will still live on wherever you have the Dropbox application installed -- other computers, your smartphone, your tablet -- as well as in your Dropbox master vault, stored on Dropbox’s cloud servers.
Go after the other computers and mobile devices first. Uninstall the app, then trash and wipe the data. Then you'll need to delete your Dropbox account.
Note that you can permanently delete selected files via the Dropbox website, and the changes will be reflected on the PCs and devices that have the Dropbox app installed. Visit Dropbox.com and searching for “delete Dropbox.” There is a link that will guide you through the process.
(You may be also interested in this video about how to permanently delete a file in Dropbox, and another video tutorial that shows how to delete multiple files in Dropbox)