Also fairly round, large denomination. Even when scamming somebody as incompetent as MtGox, as a criminal I'd be more elaborate than saying "I haven't received

Also fairly round, large denomination. Even when scamming somebody as incompetent as MtGox, as a criminal I'd be more elaborate than saying "I haven't received the 5000 BTC, can you send them again?" to the same address hundreds of times. I don't think this has anything to do with it, it should be easy to determine if the transaction are linked to MtGox and malled tx's