The creator of Instapaper has a great article about a new behavior in iOS5: the "cleaning" of files put in the cache or tmp storage areas of iOS device. In a nutshell, the problem is that iOS 5's storage model doesn't accomodate the concept of files that users download for offline viewing. If you run your iOS device with a small amount of free space, you may find that your Instapaper documents have been "cleaned" from your device. Marco has already gotten notes from fellow developers who saw Instapaper files disappearing from their beta iOS 5 devices. With the general release of iOS 5, he is bracing for a flood of reports from regular customers. The tactical recommendation for users: be mindful of your free space, especially when you're about to be offline (or nearly offline) for extended periods. The strategic recommendation: consider buying iOS devices with more storage than you think you might need. I'm sure Apple recognizes this problem; I hope we won't have to wait for iOS 6 for a solution. It sounds like developers need to have a directory for files that should be protected but shouldn't be backed up to iCloud.