Younger Australians rarely use the post, whilst older ones are comfortable with it. It's the younger Australians that are more likely to want same sex marriage.
For this reason I believe the 'no' vote will win. Most of the older population will have there say but many young ones who would vote 'yes' simply won't be bothered to vote.
I think it's a joke we are wasting $ on this shit. The government is full of spineless hacks on both sides.