Remember how the discovery of a botnet took much of the value out of the Mt. Gox Bitcoin exchange, leading it to declare bankruptcy? Yeah, investors aren't happy about that -- and they're now demanding compensation. One of them, Gregory Greene, has filed a lawsuit accusing the exchange of fraud for not doing enough to protect traders from theft. He's pressing for class action status to cover all Bitcoin owners who used Mt. Gox, and he wants the exchange to pay both restitution and damages. It's not yet clear how the company will respond, but it wouldn't be surprising if there are other lawsuits to come. When customers may have lost the equivalent of $480 million in virtual currency, there's a lot more than just hurt feelings at stake.