From most Australians I've spoken to, it won't take much spam action on their parts to exhaust their (expensive) Internet plans' (very small) data caps.
There's no such thing as unlimited residential internet in Australia.
Not for $59.99 anyway - and from what I found, it is $79.99 with TPG, as you have to bundle your home phone with them. Also note the ~Limited coverage availability at selected ADSL2+ with Home Phone enabled exchange areas. Which would relate to the fact that they have to be exchanges that TPG owns, which you'll find is predominantly exclusive to Sydney (http://www.tpg.com.au/maps/).
Even with all of this, TPG is notorious for having poor service and high contention.
