It's a gray area with exploit in this sense, since the context of the paragraph in the terms of service is 'using exploits to modify any users experience...' I would say that's not what happened here. That doesn't mean that it wasn't wrong and everyone should have known it was an error, but Gree made things far worse with the way the handled it. And to call those who purchased the gold cheaters and then arbitrarily replace the gold with an amount the did not agree to rather than issuing refunds, is not only ridiculous, but I would say they are violating their own terms of service and they are engaging in a 'bait and switch.'