While in the US you can "sue anyone for anything", that's not universally true elsewhere. It's absolutely vital that if people want to litigate this they consult experienced litigation lawyers in the appropriate jurisdictions. It's not simply a matter of "pick a defendant, any defendant". It's also important to take into account that costs awards in some countries are only a proportion of the actual costs spent on litigation - you can still be out of pocket financially even if you prevail in court. The cost of suing multiple defendants across multiple jurisdictions will not be small and the process will not be a rapid one.
The lawyer I contacted works for an internationally established company with offices all around the world and experience with dealing with financial / banking lawsuits.
I think that one of the reasons people have been willing to write off losses in the past is a desire to avoid their transactions coming under legal scrutiny. Making a legally enforceable claim involves identifying yourself, and some people would rather forfeit their funds than do that.
That's all fine. Those people can still use other ways of attempting to enforce their claims if they believe it is worth it. But eventually there will be a sufficient demand for more "official" enforcement methods.