Generally your data is safe in the cloud.
You need to make sure you take precautions obviously, like using a strong password or enabling two factor verification, but generally speaking your data is safe.
‘Generally speaking’ is a long way from saying ‘always’.
For instance, I read with dismay a recent blog by an Apple Music subscriber.
This particular subscriber claimed that the music files on their computer had been uploaded to Apple’s cloud servers and then deleted from their PC. There were two problems with this. Firstly Apple converted the music files to MP3 format, which was a lower quality than the originals. Secondly, they replaced unusual or unique files (like live performances) with what they considered to be the correct versions, often getting it wrong.
You can read the full blog here: https://blog.vellumatlanta.com/2016/05/04/apple-stole-my-music-no-seriously/
Now considering the person who wrote the blog also creates their own music, you can understand why there might be a little steam coming out of their ears. Luckily, they had a full backup that they could use to restore the missing files.
We all must remember that despite calling it ‘the cloud’, our data is stored on physical servers somewhere and not just some ephemeral something up in the sky. That means however unlikely it may appear, our data is at risk to ‘acts of God.’ For example, last summer it was reported that multiple lightning strikes had hit a Google data centre in Belgium, inadvertently wiping the data of some of their customers.
Things can and do happen that are out of our control.
The good news is that it is easy to protect yourself by backing up your data to external storage of some kind. USB storage prices have come right down over the years. You can now buy a 128GB USB stick for less than £30, which makes it cheap and simple to have multiple backup drives for your important data. If that isn’t big enough for your needs, you can buy a 1 or 2 TB external hard drive for under £100.
Oh and it is important to have more than one backup, or at least to test your backups periodically. If the worst happens, you want to make sure that everything is working and that you can actually retrieve your data.