Amazon have begun to implement a remote kill-switch that removes text-to-speech functionality from their Kindle ebook reader. A byproduct of the Author's Guild TTS controversy, the system allows publishers to disable text-to-speech on a title by title basis; as of this week, TTS has been removed from over 40 works including five of the top ten Random House best-sellers in the Kindle store.
The argument from the Author's Guild is that, by artificially reading out any ebook, Amazon are impinging on audio-book rights that the copyright for Kindle texts does not cover. Amazon, meanwhile, maintain that it is a legal use of the texts, but implemented the kill-switch nonetheless to make rightsholders "more comfortable".
As Slashdot raises, Amazon has not made clear what other flags might be present in its Kindle format. While currently the Kindle DRM is known to prevent loading of the file onto non-Amazon ebook reader devices, and now to allow remote switch-off of TTS; it's possible that it could also only allow certain texts to be read once, or in certain orders.