It is obvious that CM did not do what they said they were doing
To be honest, I'm really confused about this whole private key thing. On one hand, they did display the following text in their FAQ:
Do you know withdrawn private key?
Sadly, yes, we have created them and as long as two people knows private key, either of them can move funds. When you withdraw a chip, you receive a copy of private key encrypted on the mixer's server.
Which, as I interpret it, it reads: "We don't delete private keys". And everything else related to the session like amount sent, amount donated, time the mixing started etc., were said to be deleted after 7 days:
Your session lasts for 7 days. After that, your session and all its data will be removed. You can also destroy your session before time is up. We keep statistical data ie. how much was donated.
But, on the other hand they did claim private key chips are deleted once the session is destroyed:
Destroying the session deletes chip private key.
Therefore, there is no reason not to justifiably suspect that the logs are part of what they got their hands on.
Going from "keeping the private keys" to "working closely with the government by doing blockchain analysis" is quite of wild jump, don't you think?