A campaign was recently launched for free public transport in Victoria. The group behind this, Free PT Victoria, had a Twitter account and a website asking you to join, but both seem to have disappeared now, despite gaining a lot of approval from some of the people in my Twitter feed. Nonetheless, they're not the first to push for this and they won't be the last.
The website didn't seem to have any kind of detail on why they think it's a good idea, or how it would work. This is not that surprising, really, as people who advocate free public transport seem to think that it's fairly self-evident why we should have it - just as many of those who think we should pay for it think that's self-evident. So I think it's still worth exploring.