This change to your policy is absolutely unacceptable. I've trusted Evernote for years with very sensitive information thanks to its support for 2-factor authentication and HTTPS over the web app - hundreds of notes that contain private and proprietary information about clients and their data. I've relied on Evernote to uphold that trust. It has been the best option for keeping these notes on hand regardless of where I am or what device I'm using, and this policy completely undermines that.
I don't care how well-credentialed and background-checked your list of authorized employees are; the fact is you're asking me to trust unknown persons to have random access to this information, or to trust in algorithms I know nothing about to be able to identify what they should and should not see, in order to test what amounts to a toy.
It's my job to decide who should and should not have access to this information, not yours. The only situations where anyone should be granted access to my data are with my specific prior approval or under legal obligation.
If you can't test your machine learning algorithms in a developer sandbox using test data that hasn't been filched from unauthorized private sources, you are not ready to be playing with these tools.
For once I'm thankful the tech media started a panic, or I wouldn't have known to opt out - and I'm still wary of the other reasons you might choose to access my notes without authorization. It's a shame I even have to, since I'd like to see what you do with machine learning, but I don't see any way to opt out of snooping while opting in to the features you claim to need it in order to support. Worse yet, as a Linux and Android user exclusively, I can't even use your built-in encryption tools to protect sensitive notes on a per-item basis since you haven't bothered to support it on my platforms.
This is the worst in a series of unilateral decisions over the past year or so that have undermined my faith in your credibility and wisdom in moving Evernote forward. I understand you're under a lot of financial pressure but I can't understand how you thought doing this, especially in order to support a feature of dubious value, was supposed to help. I've come to the point where instead of considering upgrading my account in order to support you financially (despite not needing any of the things on offer in your paid tiers), I'm actively looking for a replacement for Evernote and no longer recommending it to friends and clients. What a shame.