I'm not familiar with Dutch law either, nor have I studied the particular case you are referring to, but with respect to the "virtual property" issue in general, I would suggest a comparison with financial assets deposited with a bank (the virtual world operator). If someone, somehow, either forced you to transfer a particular amount from your account, or misappropriated that amount without any confirmation from you, would that constitute either "theft" or "fraud" in the eye of the court? Who would be the victim of that crime, you (as the legal owner of the assets) or your bank (as the involuntary mediator of the irregular transfer)?

This analogy is probably only valid for a limited number of situations which may arise in a virtual world setting, but I consider it relevant as money constitutes the typical measure for both labour and physical goods.