Here's something that has been brought up earlier on this thread, but worth mentioning and clarifying further because it's essential for everyone involved to understand it fully:
The judge in the case, Masumi Kurachi, ruled that the Japanese law only allowed for proprietorship of tangible entities that occupy space and which allow for exclusive control over them.
As a result, virtual currency could not be owned.
What's at stake is that when we (as MtGox clients) sent our BTCs to their exchange, those BTCs are no longer ours. What we have instead is a licence agreement (or if you prefer, a "promise" of MtGox) that will give our BTCs back whenever we want to withdraw them out of there.
This is not limited to MtGox, but involves
EVERY EXCHANGE out there. Meaning that every trader should be aware that whenever he has deposited his crypto on an exchange this crypto is *literally* not his. What we expect here, (more likely wish for) is our *possibility* of getting a fraction of our crypto. This should be considered equal to the possibility of us, not getting anything at all...
I did not even bother to request the BTC I had in Mt. Gox. That was minor in my case because I sensed trouble and drew down my BTC account to a minimal level. I did file a claim for the wire they never sent after I sold some BTC for fiat on Kraphole's trading platform. This ruling is actually great news for people in my situation because it indicates that it is unlikely that whatever fiat value can be clawed back will be converted back to BTC to make whole those who have (or don't have) a claim in that medium.
Note that the same principle (value becomes property of the depositee upon deposit) applies to fiat in banking institutions in the U.S. As I understand the law at least. Just as I always limited the BTC I had with an exchange (even back in 2011) I limit the fiat I keep on deposit in a bank. Same legal and operational rational, although bank failures are vastly more rare than appropriation of BTC by Bitcoin exchange 'services' so I am usually prone to keep more value under such risk in mainstream banks.
I very much look forward to the continued development of the 'trust everyone' frameworks being undertaken by the Blockstream guys. In this way I could store value at an exchange and they would have an arbitrarily limited ability to appropriate it, or at least to do so indefinitely. In such a world the court's word on such things becomes irrelevant.