Dropbox is a wildly popular service that automatically makes backup copies of your files and copies them to other computers, such as from your desktop computer to the laptop or from the office computer to your home PC. However, some people are nervous about using Dropbox because it also keeps a copy of your files on Dropbox's servers. Actually, I think that is a good thing but I also know that many people disagree with me; they don't want their personal files stored on anyone else's servers.
Now BitTorrent Inc. has launched BitTorrent Sync, a pre-Alpha service for syncing files between devices. The new service is very much like Dropbox but with one major difference: it doesn't store any files on anyone else's servers. In fact, it doesn't store any files anywhere in the cloud. It only copies files directly from one computer you own to another computer you own (or to a friend's computer that you explicitly allow into your personal "network") without intermediate storage anywhere else. This is accomplished by using peer-to-peer technology: all files are copied directly from one of your computers to another of your computers with no intermediate servers involved.
NOTE: BitTorrent Inc. is best known for its peer-to-peer file transfer technology that avoids intermediate servers. The new BitTorrent Sync obviously is built on the same technology. BitTorrent software is completely legal but is often used for illegal purposes, such as downloading movies and music. As such, I suspect many people will decide to avoid BitTorrent. However, the same software is also often used legally for distributing huge files without overloading servers.The pre-alpha program is open to a limited number of users. Anyone who signs up is warned that pre-alpha software is almost guaranteed to be buggy. Pre-alpha users agree to help in testing and debugging the software and to provide feedback to the software developers. If you expect everything to work perfectly, I'd suggest you stay away from BitTorrent Sync until after the company releases a production version some months from now. However, for anyone who likes to be in on the "ground floor" and is willing to test for bugs, this could be an interesting project.
As for me, I think I'll wait for a later release.
You can read more on the Official BitTorrent Blog at http://blog.bittorrent.com/2013/01/24/test-bittorrent-sync-pre-alpha/ and at the new software's forum at http://forum.bittorrent.com/forum/56-bittorrent-sync/.
You can sign up for the test at http://labs.bittorrent.com/experiments/sync.html.