With iCloud now on the Mac as well as the iPhone and iPad, the ugly suprises keep coming, as Ted Landau explains:
If you use iWork applications (Pages, Numbers, Keynote), you can use the iWork section of iCloud to sync your documents across all of your devices—Mac OS X and iOS. Sort of. While it generally works well when syncing documents among iOS devices, syncing to and from Macs is another story. Even when syncing among iOS devices, there is potential danger—including a chance that all of your documents will vanish.
-Macworld, October 21, 2011