Trade marks allow brands to work, but what if a brand or product name becomes so big its core word takes on the title of another product, not owned by the company who invented that name? Take the iPod. There are now many variations on the word applied to accesories, spin off products and entire generations that use the product.
But now it seems, Apple are claiming rights to the word "podcast". Podcasts are seen in the market place as online, downloadable radio programs for use with any mp3 player but Apple are of the belief they own the word as part of their "iPod" trademark..... hmmmm sounds like someone at Apple didn't make the call to the patent lawyer soon enough too me.
Podcasts are everywhere and Apple what the revenue associated with the name. They recently handed the owners of www.podcastready.com a forceful please explain letter (it was more of a "cease and desist" really) for the use of the words "podcast ready" and "mypodder".
My opinion - your trade mark is for "iPod" Mr Jobs, you can't win 'em all.*
* I have no qualification to allow me to decide on trademark law issues, (studied it at uni in marketing law but I don't think that counts when taking on Apple).