A new threat called, "BadUSB" can be executed from any USB device, not just flash or backup drives (eg: USB keyboards).
To make matters worse, currently there is no way to defend yourself against the potential threat other than not to use USB devices.
Sure, you can use cloud storage for your non-sensitive data instead of USB backup drives. However, I don't trust storing my sensitive data where other people have access to it. Nor do I want to find out the place I chose to use ended up being the next place to be breached leaving your data vulnerable.
Even worse, BadUSB remains imperceptible to antivirus software and mobile security apps, and lives on even after the contents of the drive and devices have been deleted and reformatted. -Sara Angeles