[added later] Another theft of some 250,000 USD has occurred at another Chinese exchange on 27 Jan 2015. Here some Internet posts claim that the thief has transferred money to this address. However questions remain: how is it possible that one given thief has managed to steal exactly 1000 BTC?
Possibly bitcoins could have been stolen using one of advanced private key recovery attacks described in our recent paper. However this is far from being certain. There are many much simpler methods to steal bitcoins. There will be a seminar about this at UCL on 26 February 2015 at 16h-17h, room MPEB1.03, see here and here are some slides about this and about bitcoin wallets and here are a list of known repeated random events.
In the BTER case the victim company has offered a bounty of 720 BTC or some 170000 USD for anyone who would help in the retrieval of stolen bitcoins.