Developer website: Deebo
AppleIDStrip is a slick, easy tool to remove personal information from your iTunes Music Store files. It's a front-end droplet for AtomicParsley, which removes all account-related atoms from your files, including Apple ID's from AAC files.
To use it, simply drag an .m4a from iTunes--or any location--and drop it on the the app.
OS X 10.5 or later