I know this topic has been driven into the ground, but thought I'd mention one last thing that's relevant here, and also something I'm curious about. When using any of the spoofer pkgs out there, like ones from nathan r32, it doesn't even report the correct FW version to Sony. Below you can see the request sent out when spoofer is active:
User-Agent: Lediatio Lunto Ritna
X-Platform-Version: PS3_C 04.21
This is strange because you're still allowed login even though as you can see the X-I-5-Version, and X-Platform-Version parameters are incorrect. What's weird is if I set rewrite rules to change PS3_C 04.21 to PS3_C 04.30/1 it won't let me login. Not sure why that is? Anyways, my main point here is there's plenty of ways Sony can detect you're online illegitimately.. you can clear your history, etc, but I just don't think there's really any 100% stealth method to be on PSN/SEN on CFW.
EDIT: Also worth mentioning is that all installed homebrews send a request to tmdb.np.dl.playstation.net upon login. Just another potential way Sony can detect us.
GET /tmdb/RBGTLBOX2_00_69271B042E056617FAC1F0304429EBE6976FA667/RBGTLBOX2_00.xml HTTP/1.1
User-Agent PS3Application libhttp/3.5.5-000 (CellOS)