What if the platform is not registered as a business in Australia? You can't fine it if it's not a legal entity there. Simply setup a php Facebook clone and host it in another country.
Yes VPNs blah blah. But it will be pretty hard to operate some rogue social site when you can’t sell any respectable ads besides maybe porn sites and malware, and are only accessible via VPN. Pretty high barrier to adoption for a brand new site.