If you want to get a temporary IPv6 address which is not MAC based (so you do not always surf with the same address and can be tracked), you should enter
sudo sysctl -w net.inet6.ip6.use_tempaddr=1
on your Mac’s commandline. You will then get an additional temporary IPv6 address which does not reveal your network card’s MAC address as part of it. This gives a bit more privacy!
Should also work on iPhone/iPad in case of a JB!