Evernote recently announced, that some user’s note will be subject to a machine learning process.
Although they claim to stuck to their Three Laws of Data protection, but the update is, that a Evernote employee may read your notes in order to check and validate the machine learning algorithms.
I personally do not like to have a machine read through my notes. There are other applications, where this might be useful, but not for my notes.
You can opt-out from this program in your personal settings:
[UPDATE]
It seems that Evernote has changed the strategy to opt-in.
As a reminder: you can always encrypt part of your note with a password. Unfortunately you cannot encrypt a whole note or notebook at this moment.