Earlier quoted context omitted.
They're also problematic because you'll likely optimize for whatever metric you pick with no regard to the ethics of the optimization. Sometimes a double blind test is not the right thing to do.
I've never really bought this argument. There might be unethical growth hackers in the company, but A/B tests are not the problem in that situation. In my experience, they mostly just catch bugs. Stuff like "hmm, our much better looking signup flow underperforms... oh, the form is broken on Safari." That kind of thing.
This can be the case for A/B testing. Sure, you can increase ad clicks by 30% ... if you trick the user into clicking it through a carefully timed layout jump.
I think GP's argumentation may go in this direction. I'd probably not say A/B testing is the problem itself, it is a tool after all, but I could imagine it's sometimes not used very well.
Another point: Spotify's core flow changes so much (feels like almost daily) that I've lost all confidence in using it.