I'm saddened to see Dropbox on the list. Did they choose to participate or is it mandatory?
In any case, we've moved several projects to BTSync recently from Dropbox (for no other reason than to free up space on Dropbox for our personal files) and have been enjoying the service.
As a p2p encrypted protocol, I imagine it's much more difficult to eavesdrop on your files and would actually require a warrant to obtain.
The government's theory is that a national security letter is sufficient to get access to your data. No warrant required. And Dropbox is not allowed to tell you that it happened.
The ability to detect duplication in no way proves the files are unencrypted (indeed this should be obvious from the fact that there is only negligible network traffic to confirm a duplicate! The bits can't be compared if they're not transmitted.)
It's the ability to serve deduplicated files that brings the service into question. Yet I wouldn't be surprised if there exists an asymmetric encryption method which permits decryption with one of several private keys – if so, secure deduplication is trivial: confirm the duplicate using a hash or comparing public-key encrypted versions; re-encrypt using both original and duplicate keys.
(And let's not even forget the ability to reset a forgotten password…)
BTSync cannot handle conflicting changes. It will destroy data if a file is modified in both places, and will proceed to overwrite something when it propagates the update.
And, if you're concerned about spying - well, it is closed source.
In any case, we've moved several projects to BTSync recently from Dropbox (for no other reason than to free up space on Dropbox for our personal files) and have been enjoying the service.
As a p2p encrypted protocol, I imagine it's much more difficult to eavesdrop on your files and would actually require a warrant to obtain.
I presume that's true for AeroFS as well.