The website seems to be Polish.
According to the whois entry for this domain (see http://www.eurid.eu/) the registrar is "Domeny" (http://domeny.pl/).
The registrant is anonymous.

Maybe we could contact the registrar and inform them that one their customers is involved in fraudulent activity and request the full name and address?
I am not an expert in Polish law (European law?) but there has to be way to bring the owners to account and force them to pay out the Bitcoins to their rightful owners.
We're talking about several thousand Euros here, aren't we?