I've posted on this topic before, but as a photographer, this is a topic that's dear to my heart, and I feel it's such an important point that it's worth reiterating. Not because I want to sell prints. I already do that. But the fact that prints are my business is not what drives my motivation to print and to urge others to print. On the contrary, my drive to print is what motivates me to have a business for it.
I fully believe that a properly printed photo will far outlast the digital file that rendered it.
I also fully believe that this generation will lose more historical data than any other because they aren't grasping the above fact.
I've gotten into this debate several times with friends and family, and many people seem to believe that the digital file itself is king. When you really break it down, however, you find that all of the best archival storage options for digital information is actually quite limited compared to a properly cared for physical print. And the best part... it takes no special equipment to view a print. It's 100% available 100% of the time. Even if we were able to find a long-term storage device for digital data, the fact remains that another reading device is required to access and translate that information before it can be viewed. So, you'd better hope that 500 years down the road, a device exists that can read the stored data for your ancestors.
Most of us already understand the key to digital storage, which is redundancy. Have copies of everything in as many different places as you can. And yes, this helps, but even still it's a constant battle to upkeep the archives and make sure they stay in a format that's relevant, resulting in the same data saved to an array of different types of media storage over the years.
Another thing to consider is how much data each medium can hold. We're reaching into terabytes with memory cards now, for example. This has created a cultural "all-eggs-in-one-basket" mindset in recent years. It's conceivable to believe that someone could potentially store their entire digital lives on 4 or 5 high-capacity SD cards. Maybe fewer.
Also relevant to this topic is this very poignant printer commercial by Canon. While humorous, it brightly highlights exactly the kind of issue we face when we don't print what we want to keep.