This is already happening. I wonder if Challies hasn’t heard?
I’m not too worried over this. It’s tremendously easy to publish and distribute an ebook in nice, clean, DRM-free epub format. I get that it may affect the bottom line of those Christian luminaries who make much of their income via book sales. But I think the Church will be just fine as long as there are some Bibles available.
For those who don’t want to lose Kindle titles they’ve bought from Amazon, highly recommend becoming familiar with Calibre and the Apprentice Alf DRM scripts.
New Warhorn Media post by Tim Bayly:
Howdy, strangers! Haven’t been around for a while because summer is my crazybusy season, but I read Tim’s article and had to pop in and note that you can also buy a ton of Doug’s books from his website for a buck a piece: https://dougwils.com/store. #ShamelessMarketing
Oh, and Rosaria is RPCNA, not OPC. 
Thanks I’d corrected it
Gary DeMar just wrote a similar article inspired by the same Challies article in the OP.
Although it’s essentially the same argument Pastor Bayly makes, DeMar points out some different examples of books that are very difficult to get mainstream Christian publishers to publish.
He also points out that Amazon has significantly helped sales of small publishers, particularly in the e-book format, which is something I hadn’t really thought about.
This is an interesting article. Given some of the dreck that gets published (Joyce Meyers, anyone?), it’s interesting to read someone who sees Amazon as giving him more freedom than the Big Eva publishers.