Blacklist is the term used to designate Amazon Kindle devices that were blocked from being registered because they were refunded, replaced, reported as lost or stolen. Blocking occurs through the Serial Number. If a device has been blacklisted, it is impossible to reverse this, except on some occasions where the lost/stolen device returns to the original owner.
Blacklisted devices also have some limitations, such as not being able to change the device name, access advanced settings, access Whispernet, create collections, view Wikipedia summaries and make translations, etc. Basically the device will only be able to access the internet trough the Experimental Browser (Wi-Fi) and read sideloaded books, transferred from a PC by USB cable, in the "documents" directory, manually or using programs such as Calibre.
To update the firmware of a Blacklisted device, you have to transfer the update by USB cable, in the "Root" directory, and update the firmware in the device settings.
Remember that the use of a Blacklisted Kindle can be considered a crime, and you are responsible of all you do with it.
 Sales of Blacklisted devices
Be careful when buying a used Kindle, there are many cases in which the devices were bought blacklisted, but don't worry, this guide will help you:
 How to identify a Blacklisted Kindle
- Take a note of the Serial Number and call Amazon asking them if it's Blacklisted. You can see it in the device settings or in the back of the box;
- If it's Blacklisted, don't buy it, but if it's not, de-register it logging out from the previous owner's account, resetting the Kindle, and then registering with your account, if it registers, all right;
- Blacklisted Kindles may be sold by other people, but also by some stores.
 Stores/Websites known for selling Blacklisted Kindles
- Craigslist (US);
- Letgo (US);
- MercadoLivre/MercadoLibre (BR);
- eBay (Worldwide).