Failure rate of usb pen drives?

Do pen drives(memory sticks) have a high failure rate, also what is the correct name for them, is it flash drives or usb pen drives or are they both the same thing
Update: I found out to my cost that flash drives aren't all that good when storing important docs, i had some docs stored on a flash drive and it failed on me last week, i should put the docs on a cd/dvd or better still backed the docs up to my hard drive
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