This is the second time that BTER has been hacked in a time span of 6 months. Either they were extremely careless, or this time it was an inside job.
It's very likely to think it was an inside job. If not, they just don't care about losing 7K BTC.
Cold wallet isn't something that get hacked if stored right. From that perspective you can say it was probably an inside job.
Some people clearly can't resist the fact that they can access/steal over $1M worth of coins in just a short time.
People should stop with leaving funds on such poor secured exchanges. Keep everything in your offline wallet.