As with the other Australians I sit in the front. I don't like the back seat in any vehicle and always prefer to be in the front passengers. The last time I was overseas and caught a cab I asked the driver whether to sit in the back or front.
Recently the news here has been around the idea of "pink taxis" specifically to transport women late at night due to a number of assaults on women (I think mostly intoxicated women) by cab drivers in the last few years. By recently, I mean a recent push, I'm sure I remember this issue coming up a year or two ago as well.