This is a good reason to open it.
With an open wifi there is no good case that it was you.
With a secured wifi - you simply have to convince an 80year old judge and a jury of sheep shearers of the mechanisms of an attack on a WEP secured link.
Australia may be an extreme case but there's plenty of this desire for tight control going around. From Iran to the US, to Holland, the UK, Germany, etc.
The bottom line is, the cold war struggle between communism and capitalism is over and fascism won. Fascism briefly lost due to being on the losing side of WWII but in the long run it's clearly winning.
Everybody look at Singapore that's where we're all going. This: http://www.recombinantrecords.net/docs/2009-05-Amusing-Ourse... is about us living in a combination of 1984 and a brave new world. We (except for Singapore) aren't quite there yet in terms of government control but that's where we're headed. And because it will never be as extreme or obvious as 1984, there's no need to go that far, nobody will be rioting to stop it.
The only difference between Iran and Singapore is, Singapore's economy is strong and they don't bother with tight social restrictions.
Because they are spending millions of $ on internet spying systems and it's all pointless if the terrorists can control their kangaroos with laser beams from an open wifi.
I used to until they started using my network for bittorrent to the point that it consistently had poor performance.
I'd set something up to throttle bandwidth and restrict certain protocols from unregistered MACs, but I'm not motivated to make that much of an effort to share my network.
The thing about having an Open Wireless connection here in Australia is that we generally have caps on the amount of bandwidth our internet plans come with. Once you go over that cap, your connection becomes rate limited and it feels like you're back in the stoneage.
So, even for that reason, sharing connections here in Aus is a bad idea because all you need is one bandwidth hog to screw up your internet.
I leave my network open with a note to please not abuse it :)
I haven't had any problems yet, but I do have QoS set up to preserve the traffic I care about. Honestly, it's rare that I've had guests log in to the network. Looking at the MAC analyses it seems that it's mostly sporadic visitors with laptops and so on. Which is exactly the sort of borrowing I encourage.
This is where the FON wifi routers are designed to fit in, with a private AP for yourself and a throttled public AP. Shame the 'public' AP is only available to other FON users.
It would only take a few hours to create this set up yourself I guess, but FON is ready after being plugged in.
As a response to this if I were in Australia and I had my wi-fi locked down I'd open it up.
Terrorists, downloaders and pederasts will do their thing regardless of unsecured wifi routers.