I use it for everything that I don't need to share with other people, because it scales 'for free' with the size of my data (my music library, for instance), an

I use it for everything that I don't need to share with other people, because it scales 'for free' with the size of my data (my music library, for instance), and because I can use it across many different devices but selectively sync different 'types' of things to different devices (e.g., a large photo collection doesn't need to be on my mobile phone).