Advantages
Data stored on flash drives is impervious to scratches and dust, and flash drives are mechanically very robust making them suitable for transporting data from place to place and keeping it readily at hand.
Compared to hard drives, flash drives use little power, have no fragile moving parts, and for most capacities are small and light.
Flash drives implement the USB mass storage device class so that most modern operating systems can read and write to them without installing device drivers. The flash drives present a simple block-structured logical unit to the host operating system, hiding the individual complex implementation details of the various underlying flash memory devices. The operating system can use any file system or block addressing scheme. Some computers can boot up from flash drives.
Specially manufactured flash drives are available that have a tough rubber or metal casing designed to be waterproof and virtually "unbreakable". These flash drives retain their memory even after being submerged in water, even through a machine wash. Leaving such a flash drive out to dry completely before allowing current to run through it has been known to result in a working drive with no future problems.
Disadvantages
Like all flash memory devices, flash drives can sustain only a limited number of write and erase cycles before the drive fails. This should be a consideration when using a flash drive to run application software or an operating system. To address this, as well as space limitations, some developers have produced special versions of operating systems (such as Linux in Live USB or commonplace applications (such as Mozilla firefox) designed to run from flash drives. These are typically optimized for size and configured to place temporary or intermediate files in the computer's main RAM rather than store them temporarily on the flash drive.
Most USB flash drives do not include a write-protect mechanism, although some have a switch on the housing of the drive itself to keep the host computer from writing or modifying data on the drive. Write-protection makes a device suitable for repairing virus-contaminated host computers without risk of infecting the USB flash drive itself.
A drawback to the small size is that they are easily misplaced, left behind, or otherwise lost. This is a particular problem if the data they contain are sensitive. As a consequence, some manufacturers have added encryption hardware to their drives—although software encryption systems which can be used in conjunction with any mass storage medium achieve the same thing, Most drives can be attached to keychains, necklaces and lanyards. The USB plug is usually fitted with a removable and easily lost protective cap, or is retractable.
USB flash drives are more expensive per unit of storage than large hard drives, but are less expensive in capacities of a few tens of gigabytes as of 2011. Maximum available capacity is increasing with time, but is less than larger hard drives. This balance is changing, but the rate of change is slowing.
LIVE USB
A live USB is a USB flash drive or a USB external hard disk drive containing a full operating system which can be booted. Live USBs are closely related to live CDs, but sometimes have the ability to persistently save settings and permanently install software packages back onto the USB device. Like live CDs, live USBs can be used in embedded systems for system administration, data recovery, or the testing of operating system distributions without committing to a permanent installation on the local hard disk drive. Many operating systems including Mac OS 9, Mac OS X, Microsoft Windows XP Embedded and many of the Linux distributions and BSDs can also be used from a USB flash drive.