Any author publishing via Amazon's Kindle needs to be aware of what is going on in Kindle world. By pure chance I picked up this info by finding a link to a blog I have not read before, but will from now on.
The link is here. It is a very long article, with important links at the end of it. Basically it is all about how people are cheating the Kindle Unlimited system and earning lots of money with nasty tricks. Sometimes I think ignorance is bliss, but not in this case - it's as well to know what is going on even if you decide to do nothing about it.