Although data is pretty safe in the cloud there still is a possibility of the data being lost in the cloud.
But when you have data in the cloud environment your data is not only hosted or stored on one hard drive but instead your data is spread among several different hard drives and web servers to prevent data loss.
In the even that a servers hard drive crashes your data can usually be still accessed because it's on another hard drive as well.
But even then it's still a good idea to have your data stored on an external hard drive, in your computer, and on the cloud storage.
Having multiple backups of data is very important but your data is likely safer in the cloud than it is on an external hard drive at home.
I keep my files including my websites database files and pictures etc in the cloud storage as well as on my computer and external hard drives just in case something happens and I lose the data on one of the storage options.
My website is also hosted using cloud hosting which helps keep it up in the event that one of the servers goes down the website can then be accessed from a different server that is still operational.