Main reason to change MAC address is to be able to join Wi-Fi networks that have whitelisting.You could also use it to simplify device administration on your network.Beyond that I can also imagine a few black-hat reasons to do itAtrix is one of the few smartphones that can pull it off easily though, others I am aware of are the LG Optimus One and the SGS series (although it's not so easy on SGS)There are plenty of other interesting datas in /pds, it is the device provisioning partition (NVRAM) and is equivalent to /efs on the i9000/Captivate (which is the last device I used, so easy for me to compare with)Careful messing with it though, on the Captivate changing the wrong bit would kill your cellular radio until you restored an EFS backup, I suspect the same danger is here with the Atrix too! And we don't have a quick way to restore a PDS backup yet like with odin on SGS (although I am hot on the heels of a method to do so)