
Re: Are Audio Books Harmful?
My personal opinions: The reason that TV and movies are not as beneficial as reading is because there is no use of the mind to imagine what's happening - it's given to you audibly and visibly, so you are a passive viewer. When you read, your mind is translating the words into audio and visuals, so you are actively engaging with the work.
With audio books, you may not be translating words into audio, but you are still converting words into mental images. Therefore you are still actively engaging your mind.
My own problem with audio books is that they make me think of something, and my mind digresses. With a book, I stop reading while I think. With audio, I forget to pause and so I end up missing chunks of the material.

If you're interested in research on the subject, you might check out:
Beers, K. (1998). Listen while you read: Struggling readers and audiobooks. School Library Journal, 44(4), 30-35.
Casberque, R.M. and Harris, K. (1996). Listening and literacy: Audiobooks in the reading program. Reading Horizons, 37(1), 48-59.
Reitsma, P. (1988). Reading practice for beginners: Effects of guided reading, reading-while-listening, and independent reading with computer-based speech feedback. Reading Research Quarterly, 23(2), 219-235.