Bitcoin is to be taxed as an asset not a currency in Australia.
The original gizmodo[0] piece has more on this:
The hacker-tipster also included multiple PDF files that contain what appear to be a transcript of a meeting about Bitcoin regulation between Wright, his attorney, and the Australian Taxation Office (ATO), as well as the minutes of a subsequent meeting of the ATO and Wright’s attorney. Wright appears to have been trying to persuade the Australian government to treat his Bitcoin holdings as currency, as opposed to an asset subject to greater taxation. Without this regulatory move, his business interests would be scuttled. During an interlude in one such meeting, Wright makes an oddly casual admission of his identity as Satoshi (highlighting added):
A request to confirm the authenticity of the document sent to Auscript, the transcription service whose logo appears at the top of the file, was denied on the basis of company policy. A request sent to the ATO was also denied on the basis of state confidentiality.
[0] http://gizmodo.com/this-australian-says-he-and-his-dead-frie...
I speculate this tax ruling and the ongoing investigation was also the reason why he wanted to migrate to the UK soon. The article has probably given the ATO reason to believe that he is under flight-risk.