The effect, very often, is to force anybody with specific reading habits to buy Amazon or be unable to read their books. This is especially bad if you don't just buy books, but read through the library or especially if you get ARCs (advance reader copies, for pre-release reviews). Advance readers who don't have Kindle are jerked around constantly by DRM and especially changes in DRM schemes. It's really hard to not see this as collusion, as it suspiciously always works for the benefit of Amazon and the detriment of every single other person and company involved.
> how is it bad behavior to say you’ll issue a takedown notice if your copyright material is republished
It's not. That's not what happened here, though.
It is bad behavior when you threaten legal action against somebody working within their rights to legally allow people to read things that they paid for on devices that they've paid for. The DMCA has specific carve-outs for interoperability. Threatening legal action there is bully behavior. I'd argue that the ethics are pretty clear-cut here too. A ton of copyright law is incredibly badly balanced against the consumer and even against small artists in favor of the biggest players. If this was illegal, it would be the law that is unethical.
> how is it bad behavior to say you’ll issue a takedown notice if your copyright material is republished
It's not. That's not what happened here, though.
It is bad behavior when you threaten legal action against somebody working within their rights to legally allow people to read things that they paid for on devices that they've paid for. The DMCA has specific carve-outs for interoperability. Threatening legal action there is bully behavior. I'd argue that the ethics are pretty clear-cut here too. A ton of copyright law is incredibly badly balanced against the consumer and even against small artists in favor of the biggest players. If this was illegal, it would be the law that is unethical.