Question on folders to exclude from Time Machine backup

[donawalt]

Hi all, I am trying to streamline my Time Machine backup a little, so I excluded some folders. I just wanted to see if I was missing any dangers from excluding these folders from backup:

1. Downloads - I never have anything in there I care about, I move a file somewhere else if it's important;
2. Dropbox - this is sync'd to a server, I can create a new machine and sync once I log in, and I can retrieve files through a browser, so no need to back it up;
3. Music - all my music is sync'd to the cloud through Apple Music subscription, and I don't really use ratings, tags, etc; (not even sure if they are sync'd but don't really care);
4. Pictures - all sync'd to iCloud.

Thanks!

 

[Wando64]

Everything that is synched to the cloud (whether iCloud, Dropbox, OneDrive, etc…) is replicated to all your devices.
Consider the implications of this. If a file, or a number of them, get corrupted or maliciously encrypted (by ransomeware for example), they will be very quickly replicated everywhere, quite possibly before you notice that there is a problem.
They will also be backed up to Time Machine in their corrupted status, however the beauty of TM is that you will have a history and therefore you can refer back to a previous version, before the corruption occurred.
I back up everything to my TM. (On two disks in rotation)
Storage is cheap, data is precious.

 

[donawalt]

Good point thanks @Wando64 !

 

[Honza1]

Everything that is synched to the cloud (whether iCloud, Dropbox, OneDrive, etc…) is replicated to all your devices.
Consider the implications of this. If a file, or a number of them, get corrupted or maliciously encrypted (by ransomeware for example), they will be very quickly replicated everywhere, quite possibly before you notice that there is a problem.
They will also be backed up to Time Machine in their corrupted status, however the beauty of TM is that you will have a history and therefore you can refer back to a previous version, before the corruption occurred.
I back up everything to my TM. (On two disks in rotation)
Storage is cheap, data is precious.

This is one of the best short justifications for using TM (or similar system) I have seen in some time.
There are more good suggestions to follow... The primary one is, that the two TM backup disks should not be in the same place as then one disaster can take away original and backups.
Minor point - some cloud systems have also version control. Depending on plan you have, you may be able to go back in time there also. But you need to check what the policy is - is it time, number of versions, etc... It all varies and can change.
BUT : Having your own backup you can take in your hands is very satisfying. It calms the panic attack you have when you have to deal with major drive crash