That's not entirely true. You can disable iCloud syncing for individual Apple apps, but 3rd party apps are all-or-nothing. You can't disable iCloud syncing for a single 3rd party app.
(That's a serious question, BTW. I would check it myself but I can't upgrade to iOS5 until I figure out how to get Windows DEP to stop killing iTunes 10.5 every time I launch it.)
Settings > iCloud > Storage and Backup > Manage Storage > [DEVICE] > Backup Options.