I can't believe this isn't possible. Evernote has been around forever and still hasn't been able to make this simple change. I have been holding up on getting premium until I see more features, the most important to me being the ability to password protect a single folder. I would buy it immediately and I believe many others would if password protecting notes and notebooks, especially notebooks, were available.
I'm sure everyone is like myself in that they have dozens of userids and passwords to sites, etc. Keeping all this in a single notebook that is secure would be a big help in managing them. You could look them up any time, anywhere if they were on Evernote. Thanks.