I think password protecting individual notes is CRITICAL. I would like to be able to store password info and possibly credit card info that I have to use for specific client projects, but I don't want to risk it being discovered. I was a devoted Palm user and it had a great feature where you could lock an individual memo and assign a password to it by just checking a little privacy box next to the memo's title. On my phone the memo would show up in the list of all memos, but its title (i.e. "My Client's Credit Card Numbers") would be grayed out (as in a solid gray bar, not simply grayed out text) so that no hint would be given as to what the content of the memo was. In order to open the memo and access it's information I would have to type in a password that I had assigned. This was an excellent, and to my mind, critical, feature that I would love to see it implemented in Evernote.
I know that it is possible to password protect an entire Evernote database, but being able to add an extra layer of an additional password for special notes would make an already awesome program even awesomer!