From an article, “Thinking about syncing,” that I wrote a few months ago:
There are a few apps out there which allow you to mount a cloud sync service’s storage as a networked pseudo-drive, rather than sync with files that live on your device’s local storage. The idea is that you can store a lot more stuff than your local storage will allow, since files so stored are only in the cloud. I tried three such apps: CloudMounter, Mountain Duck, and the promising but beta-level-buggy Strongsync. While each has its use case and is geekily interesting, each also has just enough quirks that I’d fear for the safety of my files. (Some of the quirks are just plain annoying, such as how CloudMounter’s and Mountain Duck’s otherwise intriguing encryption features change files’ modification dates. Not cool.) After all, each cloud sync service expects you to use its app, not a third-party app, to deal with whatever you store on the service; guess how little help you’ll get from that service if one of these apps FUBARs your content on the service.