Also, theoretically, it could be a single (or a few) developers going rogue, rather than an approved company policy. It wouldn't be the first time.[0]
[0] http://www.tomsguide.com/us/David-Barksdale-Google-Engineer-...
Collecting "metadata" such as Address X stored on Computer Y on ip address Z could be worth quite alot to likes of NSA who I am sure have plenty of incentive to monitor crypto-currencies and would either pay Dropbox to do it or alternatively bang them over the head with a hammer and make them their bitches in order to collect all sorts of juicy "metadata" on millions of people world wide.
Hell access to so much information could make for quite a political tool, remember that general in washington who was kicked out because he was having an affair and somehow his private communications via gmail drafts became public. What would prevent an opportunistic dictator from gaining absolute control over political landscape of a country if this dictator has access/control to an organization such as NSA?
Americans get up in arms over their right to be armed all the time, but they ignore (or do not realize?) that without privacy and secure communications they would never be able to organize a resistance to a totalitarian government which is better armed and could potentially (already does?) monitor everything and everyone on a scale that would make Orwell blush and spin in his grave.
Dropbox has already closed hundreds of millions of venture capital money at a valuation of $10 billion. I think it's safe to say Dropbox has found some wallets that are much easier to open than bitcoin wallet files. :)
"It is incredibly hard for me to believe that Dropbox has sneakily transferred >1TB"
Did they transfer hashes? name+type+size for fingerprinting? Searching for credit numbers or SSNs? Who knows. I don't. And don't do evil is no longer the basic assumption.