Penfoldian
I agree that this issue doesn't seem to have been discussed enough in banning threads, but who exactly is confusing region and video mode issues?
It seems that the lack of discussion on the subject has led to a lack of std nomenclature on the issue.
If you read my posts above you'll see that I say US NTSC (US region, NTSC video mode).
As already discussed, changes in these modes after you have connected to Live (or changes compared to your xbox's state when you signed up/used account recoverey) could easily be picked up and used to identify a modded xbox.
But it seems that the lack of discussion is because no one seems to have been banned because of this yet.
I guess it doesn't involve the use of signed M$ code in a program, so isn't strictly illegal?
I have a mixture of UK PAL and US NTSC games, but only my US NTSC games are Live ones.
Gumba
I really should pop down Blockbuster and rent UK PAL Halo 2 or something to run a test.
I can say that I've used Live often with US NTSC games using PAL video output, whilst switching region to play UK PAL games offline regularly and occasionally changing video mode to NTSC to play with my Dads HDTV projector (online & offline).
Comments so far indicate that there is no evidence for a ban based on these issues, so we are safe so far. If I'm correct on the signed M$ code issue there will likely never be a ban based on this, but I could be wrong.