What are the advantages and disadvantages of a USB Flash drive?

Items can be moved on and off of them, unlike a CD, when you burn an item, it burns it and no items can be put back onto it. Plus, they are small and portable, unlike a CD. They also come in 16 gigabyte forms, with DVDs only going up to 4.7 gigabytes, and CDs going up to only 750 megabytes.