Regarding this paranoid fear that Parliament might screw us over if it becomes too popular: There's no tax in it anyway, in the comparative scale of how our government gets its revenue. It would cost more to put it through parliament, then into the public eye via media campaigns, than the funds they would receive per annum.
They would need to consider the annual consumer spend relative to HB, then agree on a potential tax they would wallop on HB products, then comtemplate the effort required to float the legislation for consideration. Is it really worth that much to the government ? I dont think so.
And at worst, it means it can only be passed on hops. As mentioned earlier, they can't ban barley grains or yeast due to other industries need for base products. Probably not even liquid malt. It just means that the more dedicated kitters & extracters would step up to AG. That would cause a huge drop off in the number of Aussie HB'ers (of which population cannot be determined by this thread it seems!)
Hold onto your hats, I'm about to rip out some more calculations. And be very generous in my assumptions. Let's say as a hypothetical stab that there are 100,000 active home brewers, and 10,000 of them are doing AG (inflated? You tell me). Of the remaining 90,000, 25%, or a whopping 22,500 people are driven down the AG path due to the massive taxes. A further 25%, or 22,500 of people maintain their supermarket kit purchases and pay, lets say double the price of a prepared kit can (isnt present alcohol tax more like 60%, not including import excise? The Govt might use that as a model). All of a sudden for this group, buying a case of ready-made 'almost-as-good' beer seems an easier option for only a few bucks more, so let's say 1/2 of them drop off the HB statistics within a year. We're left with 11,250 kit people getting ripped off, 22,500 new AG'ers and 10,000 existing AG'ers, for whom nothing has changed. We're left with 43,750 home brewers from a 100,000 starting point.
So if they can only impose a huge tax on the 11,250 people buying kits (remember, they can't do much about the retail price of barley or yeast) and those people do one kit a month on average, and cans hike to $25 each, their spend for the fiscal year would be $300 each, or a national total retail spend of almost 3.4 million dollars. On the hypothetical 60% tax model, the goverment stands to make around two million dollars a year. I really don't think it's worth it to them to try and launch such a tax law for such a pithy return.
The only stranglehold they could truly impose is on our friend the Humulus lupus, and therefore force EVERY SINGLE HOME BREWER, regardless of method, to pay an exhorbitant retail price for hops. Doubtful that I'll be seeing this happen in my lifetime. They would need to declare the entire species a controlled substance, perhaps in the way tobacco is grown under licence & strict scrutiny, and legally administered by the ATO. All the wonderful imports would also have to pass through AQIS regulations, and probably be rejected as a threat to locally produced agriculture (ranches of POR as far as the eye can see!). One again, there's not enough impetus for the government to control it.
So in summary, I think our hobby is safe for a while longer.