Before 10.7.3 the somewhat hidden iCloud Documents folder …
… was a nice DropBox alternative to keep personal data on several Macs in sync. GoodReader on iOS also used that mechanism to synchronize files between GoodReader installations on different iOS devices and the Mac(s) of the user. The latest Mac OS X update 10.7.3 seems to have broken that feature. The folder on the Mac remains empty.
Update 14.02.2011: It looks like Apple has solved the problem. Sync is working again for me.
Update 21.02.2011: If you read the comments you’ll see the problem is not really solved. What can be said so far is that the sync problems are rather related to a bug in Mac OS X 10.7.3 than Apple wanting to keep us from using this nice DropBox-like feature. Workaround after the break…
ubd, the ubiquity daemon, is the software part in Lion to keep the Mobile Documents folder synchronized with iCloud. It resides hidden in …
The interesting observation about ubd is that Mobile Documents-syncing works immediately again if you launch that daemon on the command line (Terminal), though the man-Page for ubd states “users should not run ubd manually“… 😉
Open the Terminal (Applications -> Utilities) and type or copy and paste:
while true; do /System/Library/PrivateFrameworks/Ubiquity.framework/Versions/A/Support/ubd; done
… and press enter. As long as the Terminal remains open this should keep Mobile Documents-sync working.