A couple of years ago Amazon incorporated Audible audiobooks on the Amazon Kindle. All of the current and previous generation models have an audiobook player and you can listen to them with a pair of wireless headphones. There is an Audible shop, next to the Kindle store, where a wide selection of audio content is available. Amazon does not let you sideload in your own audiobook collection, because the audiobook player only recognizes Audible books. Should Amazon let users sideload in their own audiobooks, like they let people do with ebooks in various Kindle friendly formats?
Audible audiobooks have their own proprietary formats called Format 4, AAX, AAX+ and AAXC, although they soon we only delivering downloads in an uncrackable format. The vast majority of audiobooks that you download online are in MP3. There are various online converters that will change an MP3 to popular Audible formats, but when you sideload them on your Kindle, the player doesn’t recognize them. This is because most of these formats are basically encoded .m4b files without DRM and not encrypted with your own key.
Amazon has always supported sideloading in your Kindle books. You can download them online in the MOBI or AZW formats. Alternatively you can convert an EPUB to a Kindle friendly format using a convertor such as Calibre. Should Amazon allow users to download audiobooks and sideload them too? The Audible store is only in select markets, and not all countries. This means even though the Kindle has an audiobook player and Bluetooth, Amazon has not unlocked it for most countries due to licensing issues, sideloading content would give someone something else to do on their Kindle, aside from just reading ebooks.