Did you know that you're probably not allowed to make backups of your computer? It's true, if you believe in the legal fiction known as "End User License Agreements" (or EULAs), which are those annoyingly long contracts where you have to click "I Agree" before you're allowed to install some program or another.
For example, here's a snippet of the Adobe Integrated Runtime (AIR) End User License Agreement:
2.3 Backup Copy. You may make one backup copy of the Software, provided your backup copy is not installed or used on any computer.
Nice, huh? If you install this software, its EULA forbids you from making more than one backup copy. This is a deal-breaker for business which keep multiple backup archives from days, weeks, and months past. According to this agreement, you could hypothetically alter your corporate storage system to ignore each of the files that would be installed, but realistically no one would ever even attempt this.
This is just one more reason to be grateful that EULAs are almost universally believed to be legally unenforcable. However, unless you're willing to tell a jury that you don't think you're bound by such an agreement, remember that every piece of software with a similar license is a potential time bomb. Theoretically, you could be sued just for having it, even if you probably wouldn't be found liable.
Fans of commercial software often talk about the "impracticality" of Free or Open Source Software, but the alternatives are starting to look a lot worse.