Amazon has quietly expanded its Trade-In Program today, and it seems that a lot of you no longer want your Kindles.

Starting today, Amazon will accept your books, DVDs, video games, electronics, and now your Kindle. Send the gadgets to Amazon, and you will get a credit that you can use towards the purchase of anything sold via Amazon (including third party sellers).

While Amazon might choose to spin this as offering customers a new benefit, I suspect there’s an ulterior motive. I’ve heard of an interesting factoid that was shared over drinks at the Frankfurt Book Fair last week. Only around a third of all of the Kindle that have been sold are still in use. Turn that around and you have a vast number of Kindles sitting in closets.

Considering that Amazon has sold millions of Kindles, that number is scarily large – if it’s true.