Ask HN: Anyone on iOS 5 experiencing unwanted cellular data usage?

My friend has access to several AT&T provisioned iPhones (specifically a 3GS and an iPhone 4). Both of these devices have been upgraded to iOS 5 from Apple's public release.

As soon as an iCloud account is just associated with either device, even with all settings under Settings->iCloud and Settings->Store set to "Off" and Store purchase sync cellular usage disabled, the cellular data usage immediately starts incrementing and continues to do so.

This was measured on both devices by going into Settings->General->Usage and looking under Cellular Network Data. Prior to associating the iCloud account on either device, the "Reset Statistics" button was used and both devices were monitored to ensure that cellular usage stayed at 0 for both Sent and Received.

Starting from a clean wipe of both devices (non-jailbroken) with no software installed, no iTunes Store accounts configured, and no data usaged being detected by the statistics - once each device was paired to iCloud (even with all synchronization settings "Off" as stated above) he immediately noticed cellular data usage.

We expected this may be due to some initial synchronization it performs when the devices are configured for iCloud, however the data usage did not stop. After quite some time the statistics (both Sent and Received) kept increasing with no usage of the devices.

Total data usage after 2 hours resulted in a steady, predictable 1 kilobyte per second average usage.

To give you an idea - if your device performed this kind of data usage for 30 days, non-stop, you'd use almost 3 gigabytes in data (which is considerably more than he has for either of the data plans on these phones).

As soon as the 'Delete Account' function is used for iCloud under Settings, the cellular data usage immediately stops.

These same devices were used with iOS 4 and averaged less than 100 MBytes per month in data usage each while running it, indicating the problem seems to be new/specific to iOS 5 and not the devices themselves (otherwise he would have seen horrible phone bills).

For the sake of curiosity, we also monitored data usage when adding iMessage and iTunes App Store accounts on these devices with iOS 5. Neither of these accounts caused background data usage / counter incrementing.

... Has anyone here experienced this? Can anyone else confirm this? Thanks HN!

(If you're willing to perform the same tests, please include the phone model and cellular provider, if willing)