If the unmounting is successful (i.e. there are no error messages and Device Notifier shows that the device has been unmounted), then it is safe to unplug the device. If the device is not unmounted successfully (i.e. there are error messages or Device Notifier shows the device is still mounted), then data loss is possible if you unplug the device.
Issues Related to Hardware (Sound, Video, Printers, Scanners, Webcams, Touchpads, Keyboards, Sensors, Drives, GRUB, etc.)