Did you see my Screen Name? I am an Engineer at an ISP who designs, configures and builds large scale IP networks. I am fully aware of the IP addressing limitations.
And, yes, each Public IP is unique, otherwise the Internet would come to a crashing halt in just a few seconds. It does not matter if someone goes to IPv6, it's still a unique IP address given out by the ISP to the subscriber. Private IPs can be the same as someone else's, but that is because you can not publicly route to a private IP.
MAC address are unique. The only part that is the same is the OUI (organizationally unique identifier) that denotes a 3com NIC from a cisco router. The OUI is the first 5 characters of the mac address, leaving the other 7 to be the absolutely unique number. There are 281,474,976,710,656 combinations of mac addresses.