Unrelated to the OP, related to the extension, but doesn't this sort of thing attract Amazon's wrath, having an Associate ID set without any referrer from the project site itself?
Also, I mostly built the extension for myself so I could easily support one of my favorite podcasts. There are only about 10 other users and since I don't really plan on advertising the extension, I doubt the user-base will ever get big enough to warrant concern from Amazon.