Goodbye Dropbox (and some alternatives)

BitTorrent Sync "doesn't have a central server": can be solved by setting up a central server, e.g. on a vm somewhere.

Simple solution: encrypt your data yourself, locally, before placing the result into your dropbox folder. In fact, you should have been doing this all along, irrespective of the NSA revelations.

If you want a fairly automatic way to do so, look into encfs: http://www.arg0.net/encfs