UPDATE: PatternMusic reveals that the issue is (mis)use of the DCIM folder (digital camera image folder -- where your camera roll pictures are stored) to transfer non-image related files.

Apple, however, precludes apps from reading or writing data files to any other place except the app’s “sandbox” document folder through their developer agreement.

ORIGINAL: TechCrunch reports that the latest update to the Amazon-owned Stanza eBook reader [Free - iTunes link], version 2.1, removed USB sharing as demanded by Apple's iTunes App Store:

Just for your reference: the feature enabled users to transfer books in the ePub or eReader format to their mobile devices using a USB cable.

I’m sure Apple has good reasons to prevent people from being able to transfer files to iPhone and iPod Touch devices using a USB cable, and I believe this isn’t the first time they’ve asked developers of apps with this or similar features to remove them for new users. That said, I’m not 100% certain which rules were broken here, and since Apple requested Lexcycle not to discuss specifics we’re left guessing why Cupertino had an issue with the USB syncing features.

It will be interesting to see if a future Stanza update allows for sharing via iDisk/WebDav or Email, like other apps do to get around the sandbox.

Existing Stanza owners who want to keep the feature should, of course, ignore the update. Give us your take in the comments!

(Thanks to Fassy for the tip!)