Alright - that is one rational - but it does not answer the question of why they chose to do something that is punitive to the end user.
The answer I think is obvious: - they care more about trying to stop clones than they do about their customers. And yes it IS THEIR customers that they are impacting - because those affected thought they were buying FTDI chips.
As Dave said in the recent Amp Hour show - the onus is on FTDI to develop a technology or other means to make their chips clearly distinct and make the cloners jobs more difficult. (he suggested a holographic type label on the chip as one possible way). They are doing none of that. Instead they have chosen to take the cheap, lazy way out and change their driver in a way that affects the end user. The most this can possibly achieve to decrease clones is to do so by decreasing overall use of any FTDI type chips.
Well, step back and look it it from another direction and apply some business logic.
Because drivers don't run in userspace, the other heavily suggest option of "pop-up message" can't be done either. And system logs can be ignored. They choose the way users would most likely be alerted to the fact the have a counterfeit device, by printing out a message in the one place the driver has the direct ability to and will most likely be seen by a user.
Now, the fundamental difference between the 2 sides arguing here is this:
1) One side believes they should be able to use clones or counterfeit devices even if they are aware of them. 'If it works, it works, who cares if it's not authentic, right?' They are pissed that FTDI is taking their toys away, or that's what if feels like to them. They are using the 'poor end user who has no idea' as an example of why allowing clones to work should be a burden on FTDI.
2) The other side refuses to accept using clones or counterfeits at all. They feel when you buy from companies like FTDI, you pay more for the quality, customer service and support. You have paid more for a company that goes to the trouble to get drivers into the Windows update ecosystem so rapid deployments are easier. And you pay a supplier more to guarantee authentic parts. They are more pissed that a supplier failed by shipping knock-offs instead of the real thing. They support FTDI in their effort to identify and discourage cloning and counterfeiting.
I'm obviously in group 2. Even if a find mid production that products have clone chips in them, they come off the line. I don't care if it seems to work, or maybe even tests better. It's too risky to put trust in an unknown system.
Again, i know of one company that uses FTDI cables in the 4-5 figure magnitude. They are plugged into customer owned windows computers. They aren't batting an eye at these developments, as they trust their supply chain. They would rather have any fakes identified and replaced all at once by a mechanism like this as it is more cost effective than replacing them over time as they prematurely fail. Now I haven't heard of any of their customers reporting issues yet, but be sure if cables did come back clones, the supplier would have hell to pay.