It isn't just an opt-out option.
Even in that mythical opt-out, they still will be able to see our personal notes at least in 2 expressed terms: (a) if they suspect that there is any violation of the service by the user; (b) if the government ask.
(a) if they "suspect" there is any service violation, but in the end they find that the user didn't nothing, the damaged already will be done, they had seen the personal notes of an innocent; and who are they to lead a private investigation in users personal notes without a judicial order? It is like if you suspect of your boss (yes, we are as consumers theirs boss in the limits of the contract) and starts to read his letters trying to find something. It is a violation of our privacy and the constitutional rights that protects us.
(b) in which case they will send our notes for the government and for which government? I mean, all will need is a phone call of any agency or they will need a court order? The only legal and legitimate way to give any information for the government is after a judicial order, under the due process of law. Another question, which government will be able to ask? If the Chinese government ask for informations of an user that lives in the USA, will they provide? And if the USA government ask for information of a Russian citizen, will they give? It is not explained.
All those thing will be happening undercover, without a warning (I presume they will not be spying on us 24/7), they will see and provide personal informations without tell the users and give chance for defense. It is under the right of consumers information that before they take and after they took a tactical look in the users data, they at least send an e-mail warning.
That privacy agreement must be rethinked.
Till there I will need to find an "off line" note alternative, crypt the data base, and sync the data with Dropbox or SpiderWoak, and dell with OneNote for more simple and noncritical notes.
If I have to drop the service by a change of the company police, I will demand proportional refund, as I didn't gave the reason to finish the contract.
That's why I am a lot concerned.