I have a launch console that got banned in the very first ban wave. Since then I played offline on the banned box and online with only retail copies on a separate unbanned box. A month or two ago, right after the last update before this most recent one, when I was swapping my hard drive from the banned box to the unbanned box, my profile didn't show up. Put the hard drive back on the banned box and it showed up just fine. Tried to use a memory card to transfer it from one box to the other and it became corrupted and was then not usable on either box. I had to recover my gamertag on the unbanned box and at that point ALL of my gamesaves became unusable.
I have not tried this again since my 2nd box got banned (it has been modded for over a year but I've only been regularly playing backups on it in the last month or two since all this happened), but I am going to guess the same thing would happen if I tried to put this hard drive on an unbanned box, that my profile would again become corrupted. I'm sure they're doing this to punish people who don't care about buying a new console and only care about their profile/gamerscore. To them (I'm one of them) banning the console is only an inconvenience and a shot to the pocketbook, but not a huge deal. However, it is a big deal when you take away the ability to get achievements and kill all gamesaves, making the player start over with every game they've ever played.