Legality
Similar to modchips, the legality of these methods is disputed. While they are often advertised for their ability to make legal backups, to be used to play legal homebrew software and are considered a cheap method of development compared to purchasing official development kits, a backup device's potential for software piracy is a major concern to hardware and software manufacturers.
Companies such as Nintendo have fought long legal battles against companies like Bung Enterprises and the makers of the R4DS on the grounds that their products are used primarily for piracy and qualify as theft.
Read more about this topic: Game Backup Device