I have recently changed service cloud storage. The 7 GB available in Dropbox had I been outgrown. I changed it to Box and now its 25 GB I haven't got storage problems...
Interestingly I did not think to use the Raspberry Pi to store and sync all the files I use most on my computers, whether PC (Windows, OSX, Linux), tablets or mobile phones.
Jack Minardi gives us this tutorial to have synchronized the files at any time by the Raspberry Pi as a node.
Notice that it has nothing to do with sharing your files in the large network of torrent there on the internet, but to use this protocol to keep our files online.