**Please, please please** add this functionality!! I'm a sole proprietor, and my work requires handling confidential client information. The ability to password protect individual notebooks is a critical feature. It seems surprising (to me, at least) that this functionality hasn't been added yet -- particularly for Premium users. For the most part, I've found Evernote to be a great product. But the inability to secure individual notebooks is a serious shortcoming. (And protection at the notebook level is a bare minimum; ideally, I'd like the option of protecting individual notes). Although switching to a different app would be a real pain, this will eventually be a make-or-break feature for me.