Seriously, many of the proposals to "help law enforcement" I've seen over the last few days seem far more likely to hinder any investigation than anything else. Y'all need to step back and let investigators do their thing working within the law because if one of you idiots fucks up the legal cases against MtGox in your quest to play Ellery Queen, nobody is going to give a shit that you had "good intentions".
Good point about the potential dangers, particularly with the possible leaks of the source code and the database.
OTOH, it strikes me that freezing spending of reasonably well identified Mt. Gox accounts would be beneficial. How do you think that would harm an investigation? It strikes me as similar to evidence preservation.