Apple installers drop a .pkg file in the directory Library/Receipts whenever an Apple application or an OS update is installed. These files are used by Disk Utility to determine original file permissions (I think they're also used by Software Update). A friend had a problem repairing permissions (Disk Utility reported error -9999), which led me to check his Receipts folder. Oddly, everything in the folder before about two weeks ago was gone. Has anyone seen this problem before, or have any idea how it could happen?