I don't know how much of a place I'm in to say, not living there myself, but I don't know that it's really necessary. They seem to make you more of a target than anything (see: North Korea, Iran, Iraq, Cold War, Cuban Missile Crisis, etc.) And:
Jinx_Dragon said:
Open up a map and look at the size of Australia and how much of that land is uninhabitable.
If so much is uninhabitable and there's so little room, why would they want to invade at all? And, if I'm not mistaken, you're referring to Indonesia, or a combination of Indonesia and Papua New Guinea, neither of whom have more than about 20% [http://en.wikipedia.org/wiki/List_of_countries_by_military_expenditure] of Australia's military spending, despite the fact that Indonesia does have a larger military by number. Also, Australia is a member of the UN, and is allied with entities such as the United States, Germany, and the UK; all of whom would be willing to come to Australia's aid.
I'm not saying that places like the UK and the US deserve to have nukes and Australia doesn't, but if you can get by without them, shouldn't you try? Wouldn't a few less nuclear weapons in the world be a good thing? Just look at the Cold War and what almost happened due largely to "preemptive stockpiling"