I am not familiar with inner mechanism of Dropbox, so the following comment only comes from my daily use: Is Dropbox a storage service or sync service? I more

I am not familiar with inner mechanism of Dropbox, so the following comment only comes from my daily use: Is Dropbox a storage service or sync service? I more felt like the latter. Dropbox aggressively cache everything in your Dropbox folder into local, which would eat up the local storage space. In that sense, it doesn't provides extra storage space, rather, it provides a way to sync files between different devices, includes a S3 storage backend. Well, that maybe different from its mobile client, but on PC client, I really don't see why Dropbox will help you save your local disk storage cost (though arguably why you should save local disk storage cost since it is so cheap).