Filesystems on Linux: When Should You Not Use Ext4?

Ext4 is essentially the default filesystem on most distros, but is it always the right choice?

Filesystems on Linux: When Should You Not Use Ext4?

As with many things, a typical Linux install offers a choice of filesystems, though the Ext4 filesystem is typically the default for most distros. What are the advantages of those other filesystems, and when should you choose them instead?