Human nature has led to a consistent issue that I've experienced from computer users for my entire professional career - knowing they need to backup their data but just never getting around to doing it.
As someone that has been in the data recovery business for a very long time, we've seen virtually every scenario of data loss, which can be avoided completely with a good backup.

Ransomware is predicted to grow in scale and sophistication this year, so it's just another reason to get your critical files protected.
Any form of offsite backup is most critical to protect yourself from ransomware attacks as any type of backup that is connected to a computer when it's silently attacked will also become victimized.
The best backup systems are automatic and bug you if they aren't able to complete the task and are offsite from popular services such as Carbonite:
Home Products:http://partners.carbonite.com/datadoctors?product=Home Office Products:http://
