As Elisabeth said, generally there is no problem with used cables. I'd say that they're generally preferable, since they'll be burned-in and operating at peak effectiveness by the time you put them in the system. (Many new cables need 100-300 hours to start sounding as good as designed).
Occasionally there's a "bad batch" or bad design (like the original Monsters that corroded way up under the covering. They need to be kept dry, but problems are generally visible at or around the terminations. If there's a little corrosion right at the termination this could lead you to a great bargain, where you buy the cable dirt cheap, chop off a few inches and re-terminate. (That's a great way to buy hyperexpensive cables if you can find any flawed like that).
The thing to avoid is cables that have been in a poorly sealed basement and actually have serious corrosion. This is pretty darned rare and can be avoid generally by sticking to highly rated sellers.
Still, bottom-line is that used cables are generally and excellent deal and highly recommended.
Dave
Occasionally there's a "bad batch" or bad design (like the original Monsters that corroded way up under the covering. They need to be kept dry, but problems are generally visible at or around the terminations. If there's a little corrosion right at the termination this could lead you to a great bargain, where you buy the cable dirt cheap, chop off a few inches and re-terminate. (That's a great way to buy hyperexpensive cables if you can find any flawed like that).
The thing to avoid is cables that have been in a poorly sealed basement and actually have serious corrosion. This is pretty darned rare and can be avoid generally by sticking to highly rated sellers.
Still, bottom-line is that used cables are generally and excellent deal and highly recommended.
Dave