Memory cards are pretty tough. OK they are very tough - check out what it takes to destroy them. But why take a risk? Why not give your data the best protection you can? Over a year ago, I started using Gepe Extreme memory card cases. They are dust proof, anti static and have a rubber seal so water can't get in. They even float.
Even better they have a cunning insert (I'll bet it's patented) which allows you to put any kind of memory card in. CompactFlash, SecureDigital, SmartMedia, MemoryStick, MMC - the lot. Load up with 4 cards and one in your camera and you'll e able to shoot for weeks. I just put fresh cards label side up and full ones label side down so I know which is which. Even if I drop it from my pocket the strong latch ensures the cards don't come out.
The Gepe Extreme Card safe hold 4 cards and costs around £12. If you've been following the competitions then you know the drill by now - click here to enter a draw for one!