The louts who run Monback Brothers Trash Hauling always crush something while backing up their truck.
Backing up is critical. Having only one copy of your important stuff isn't enough. Yesterday, one of our patrons couldn't access his flash drive. "It's supposed to have a blue light," he said. But there was nothing. My flash drive worked on the same computer, so it appeared that his drive was hosed. He was distraught. Flash drives are more reliable than floppy disks or CDs, but they're not foolproof. His looked like a cheapie that you find for $9.99 in a bucket at the office store checkout. It's usually worth the extra bucks to get a good one.
With technology, anything can happen: our Internet connection could be down or slow, sunspots, Blue Meanies!! When I do a presentation that involves a live Internet connection, I always make a backup. I take screen shots of each web site and what I'm going to show there. Then I make a PowerPoint presentation and I save it on my presentation computer. Then I save a copy on my flash drive. Then I e-mail a copy to my G-mail account. Gotta do it. If someone is interested enough to attend my program, the least I can do is make sure they don't waste their time. Usually everything goes smoothly, but when I need that backup, it's reassuring to have it.