Major Nelson has warned that next week's 360 update will see the BLOCKING of 'unauthorized' Xbox 360 storage devices. By this we think he means unofficial hard-drives and also Datel's memory unit but time will tell.
Here's exactly what the Major said at his online blog:
"When Preview Program members start receiving the Xbox 360 system update next week, one of the changes is that unauthorized Memory Units will no longer work with the Xbox 360. If you’ve moved your profile or saved games onto one to “back it up,” you’d better move it back onto an authorized Xbox 360 storage device prior to taking the update. If you continue to use an unauthorized Memory Unit after the update, you will not be able to access your stored profile or saved games.
If you need help identifying officially licensed Xbox 360 storage devices or accessories you can read more about the licensed accessories program on Xbox.com"