Your data really isn't safe unless you're backing up properly and with lots of redundancy. The computer backup rule of three, also known as the Backup 3-2-1 rule, can help ensure that your data will last.
Photo by Jaymis Loveday
As Scott Hanselman points out on his blog, using just one kind of backup (eg, an external hard drive or SD card backup) is really not a backup. You need both off-site backup storage (eg, an automated cloud solution like CrashPlan), plus backups to different media types and multiple copies of everything you want to protect. Here's the old IT rule-of-thumb for backing up:
Three copies of anything you care about — Two isn't enough if it's important.
Two different formats — Example: Dropbox and DVDs, or hard drive and memory stick, or CD + CrashPlan, or more.
One off-site backup — If the house burns down, how will you get your memories back?
The Computer Backup Rule of Three [Scott Hanselman's Computer Zen]