All too frequently I modify the configuration of an existing Salesforce.com Report in the web interface, run the report, and then forget that I've made changes to the configuration and browse away, losing all those changes. It would be superb if there was a warning dialog that popped up if a user tried to navigate away from a Report with unsaved changes (like there is in the Force.com IDE if you try to close any file with unsaved changes - screenshot above). This warning would save an infinite amount of angst, head-bashing, tears, and would probably significantly reduce the load on Salesforce's reporting services since users wouldn't be rebuilding their Reports as much!