No I don't believe a brute force would work ether for the same reasons. And anyone that thinks of PS3 cloning to get back on if they get banned, please forget it, its not ever going to work.
I don't believe Sony will ban IPs, but think its more likely to be Mac address lock outs, maybe with some hardware information for more accuracy in the banning process, like motherboard version and S/n, the IBM call's S/n, user account details, plus hdd0 file allocation table, BDVD info, the list is long.
One thing is for shore, is they will change a zero to a one on your PS3, and stop loads of other things for ya, in the process when blocking that PS3 for life. There's an old saying " If I cant have you, then no one can"