ICloud syncing
I have Numbers install on my MacBook 2011 and my iOS (iPad and iPhone), and all the devices uses iCloud. Since I installes Moutain Lion, and open a spreadsheet and edit it from the mac, all the information that was in the file is lost when I reopen it on the iOS device
iPad 2 Wi-Fi, iOS 5.1.1, IPhone 4 (16 Go), MBA ('11), M.Lion