CompactFlash cards have reached ungodly sizes lately. This seems great at first --- shoot all day on a single card! --- but recently I discovered the downside: it's all-too-easy to lose an entire day's worth of photos if your card goes south.
This happened to me on a recent visit to the Denver Aquarium (incidentally, for a city that's a thousand miles inland and a mile above sea level, Denver has a shockingly well-stocked aquarium). I shot a hundred-odd photos and about a dozen video clips. Then, without warning, the card got corrupted so thoroughly that my camera actually began acting wonky, taking more than a minute to power up and power down and making it impossible to navigate the menus. The card wouldn't even mount as a drive on my USB card reader, rendering software-based disk reformatting and recovery tools useless. There are recovery services, which charge an arm and a leg to crack open your card and poke the hardware with circuit testers and such --- a mere $154 to recover a 512MB card! --- but it would almost be cheaper to buy another plane ticket to Denver and re-shoot the aquarium using a fresh card. I'll just eat the loss, I suppose, and be grateful that it wasn't my Rocky Mountain National Park pictures that got destroyed (now those would be irreplaceable).
I could carry multiple smaller cards, but I don't want to be bothered switching between memory cards during the day; plus, if one of the cards got misplaced or corrupted, I'd still lose a half day's worth of pictures.
Which brings me to my point. I'd much rather have a camera with two CompactFlash slots, and have it write one copy of each file on each card.
Of course, no digital camera maker will ever, ever sell a camera with redundant storage like this. Given how small and cheap cameras have become, this would add a lot of bulk and cost to the camera. I've experienced firsthand the frustration of losing my pictures, so I wouldn't mind, but only a vanishingly small fraction of consumers would pay for this feature.
What might happen in the future is that flash memory manufacturers and camera makers might get together and decide to make individual cards more reliable, by trading storage space for reliability. CompactFlash, like all computer storage media, contains some measures to protect against minor forms of corruption, but they could go a lot further in this respect.
In the meantime, I wonder if there are any fast, portable card-to-card duplicators out there, so that I could manually take backups of my photos while shooting "in the field"...