When is a Kindle like a $10 piece of vinyl?

Excerpt from blog entry at Bookfinder.com:

I’d like to address this by analogy. My neighborhood bookstore sells a wide variety of reading accessories. For a one-time cost of about $10, a reader can use a vinyl full-page magnifier to see the text of any book in larger print than was originally intended, effectively an unauthorized large print edition. But I’ve never seen the Authors Guild condemn bookstores for selling magnifiers.

If it’s OK to spend $10 at a bookstore to turn virtually any book ever published into a serviceable large print edition, why is it so wrong to spend $359 at Amazon.com to turn a recently purchased ebook into a poor-quality audiobook?

Full piece here.