[citation][nom]fyasko[/nom]one can change an IP but not a hexi-decimal MAC address. the MAC address is embedded in the hardware. though it is possible to flash the chip with a new MAC address it is far more difficult than changing a software based IP address. pwned![/citation]
I'm not sure why you wrote pwned, but what you wrote isn't exactly accurate. It takes about 4 seconds using freeware to spoof a MAC on a windows box. Most people who have consumer level internet don't have a static IP, they have dynamic IP, every comcast, warner, and verizon customer, unless paying extra is in this situation. That IP is subject to change and therefore is not a reliable banning method. Actually, mine changes within a week sometimes.
Spoofing a MAC on a PS3 is simply a matter of not having software developed to do it. Bc PS3 runs under a different CPU architecture, someone willing would simply need to develop software for the ps3. Something akin to Technitium MAC Address Changer, then the need for trying to flash the ps3 with another MAC is moot, you can just spoof one. The PS3 simply lacks a software to do this at the moment. But that probably wouldn't work anyway bc I hope Sony is smarter than that.
Chances are as Darkk said, when you register for PSN, Sony more than likely records both your Serial # and MAC and uses that unique combination to identify your console. I'm sure someone will try it though, so I guess we'll find out.