iCloud Tied to the Mac App Store
It’s completely an issue of trust here. If Apple hadn’t changed the rules already (they didn’t require sandboxing initially), I wouldn’t have this attitude. But since they did, then I won’t buy an app that couldn’t exit the app store gracefully if push comes to shove. The biggest barrier to such an exit is iCloud.
For my recipes, I use EagleFiler and Dropbox on the Mac and GoodReader on iOS.