Electrical current can destroy the card as well, the main culprit would be static like the shock you get when you touch a door knob on a dry day.
 | Do not touch the contacts on the back of the card. You could send a a static charge into the card and damage it. |
This is most likely overkill but I dont carry my cards in the same box as the batteries for the device. Additionally I dont let them rub against each other so static cant build up.
They are very safe in the plastic cases they are shipped in.
Possibly if you had them in a pocket with a set of metal keys you could destroy the card if the keys crossed the contacts. Common sense will keep you safe here.
I have seen postings in forums of folks who dropped cable ends on the contacts and fried a card. I looked at all my chargers and cable ends and think this would be very hard to to do. But since its out there Ill list it.
The cards a really robust and if you keep your fingers and metal objects off the contacts you should be ok.
