@amx C'mon, my NAS does not have a public facing IP. As I said, everything syncs over LAN when I am at home. I do not need sync when I am out, since I only use 1 device (my phone) at a time either way. When I come back it can sync whatever files might have changed. Until I sit down at my computer, the changes were already propagated. The only danger I see is that someone breaks into my phone and steals that file. This means discretion using the phone. Only install what I really need and only if it is trustworthy while using strict privacy guards at the same time. No FaceBook, no WhatsApp, no Games (except 2048 :D )... I am not a casual gamer to begin with.
Well, at least it's all on my own devices, which use non-standard installations and are no lucrative targets compared to some big password-paradise of a company. No one would bother breaking into them, because the time is not worth it :)