Apple recently changed their categories in iTunes. This means that every podcaster who is listed in iTunes has to take a look at their category selection and ensure that it will still work.
Many of the new categories map to the old categories, so podcasters won't have to worry about those. At least three categories have been deleted from iTunes, though, and podcasts in those categories will have to be re-jigged.
To see a copy of the letter Apple sent out, check out Audihertz.
So what's the problem? iTunes is the problem. Like Microsoft, Apple seems unable to leave a standard alone. We had a perfectly good RSS spec in place, but Apple didn't like it and added a bunch of their own tags to it. Podcasters leapt through the hoops to add these non-standard tags to their feeds because that was the only way to get into iTunes. Now Apple decides that they don't like a few names, and thousands upon thousands of podcasters now have to root through their feeds and blogware to see if they're still compliant.
Inserting iTunes tags into an RSS feed usually breaks the feed validation as well. Apple doesn't care, though. Disregarding a spec to further their own goals isn't a concern for the, sadly. iTunes would be a better product if it could read a normal, properly formatted RSS feed and require the individual podcaster to assign categories to their show. Hey...like every other directory on the planet, eh?
Companies that put their own goals ahead of the development and implementation of standards that help grow the technology sadden me. Hence why you'll never see The JaK Attack! in the iTunes music store.