Dropbox is not backup

A lot of people use cloud storage services such as DropBox, OneDrive and Google Drive. These products are great for syncing your files across multiple devices, and even accessing important files when away from your office and computer. In fact I use these products to store all my important company data. However, some people assume because they store their files in Dropbox / OneDrive / Google Drive their data is all safe and backed up, so there is no need for them to take any backups themselves. Some of these services even mention backup in their advertising. 

Just bear in mind these are primarily file syncing applications, not a file backup service. They tend to include a very basic recycle bin to allow the recovery of a recently deleted file, and sometimes the ability to recover a previous version of a file. These features are not as robust as a proper backup strategy. They will likely give some protection against file loss due to your computer hard drive failing or being stolen, but are unlikely to be a robust enough backup strategy for the majority of scenarios in which data is lost or corrupted. I have seen several instances where clients have lost or corrupted files in these cloud storage solutions, and data recovery has not been possible using the cloud services own restore features. My customers have then needed to use their own backup systems to get these files back. 

You really need a robust backup system using periodic full backups, and then frequent "incremental" or "differential" backups to capture the changes since the last full backup. This will allow the recovery of a file, folder, or everything, as it was at varying points in time over the previous weeks or months (depending on your backup retention strategy).

In summary, if you use any cloud storage system, make sure you take your own regular backups of your important data. Do not rely on these cloud services as a backup system as if you do, one day you will lose an important file or document, or possibly everything.