Something to keep an eye on:
Syncthing replaces Dropbox and BitTorrent Sync with something open, trustworthy and decentralized. Your data is your data alone and you deserve to choose where it is stored, if it is shared with some third party and how it’s transmitted over the Internet.
For now I will stick with BTSync (which has been fantastic for me, truly), but this could be promising once it gets a little further along.