Moved to Forum: Original Link
According to Myki's webpage specific to Default Fares. If you touch on while boarding a bus and "forget" to touch off when alighting in a different zone, you will only be charged a default fare which is the single zone fare.
Note : This only applies to Buses, not Trams and Trains.
I personally live in zone 2 and only take the bus once occasionly, and even if I take a bus to the city, I would often take another tram right to get where I want in the CBD anyway, so this is not useful to me. However, I'm pretty there are lots of zone 2 bus passengers out there who may find this a useful tip.
According to a Myki spokesperson : "Please note that this will only apply during the myki roll out; once the system roll out is complete the default fare for a bus trip where the route operates in both zones will change to a Zone 1 and 2 two hour fare.".
However, according the an article I once read in The Age, Myki has already cost our state AUD$1.5 Billion (more than half of NASA's US$2.5 Billion budget for the Mars Curiosity Rover Project) , so I'm crossing my fingers that the Myki technicians would not have the budget to fix this anytime soon. Lol.
Mod: Moved to forum as it's a hack / fare evasion
I'm thinking by publishing this, they will now have the incentive to fix it asap now :|