They come with the same original limited warranty that comes with new iPods, Applecare will extend that service another full year. It's fully optional to buy the Applecare but if you want coverage beyond that one year then go for it.
here's a link to the officials of the limited complimentary warranty from Apple
one of my friends bought an ipod in america and moved to germany, apple refused to service it untill he bought applecare, which he did grudgeingly, ask apple before you buy as this may have changed.