With Dropbox, can a user with a private folder create a link to a document in it without providing login and password to a third party who receives the link? I already know how to with the public file.
If you have linked accounts via shared folders then as long as you put the password file outside of a shared folder it wont sync to your friends. Just make sure that the 1Password is not in the shared folder. Usually its easiest to put the agilekeychain in the dropbox root or in a folder just off the root. The reason for this is that it makes it a lot harder to share the keychain accidentally.
If you need assistance on setting up shared folders (from your private account) to the friends then here is the sharing section https://www.dropbox.com/share
So how do you share files with others?
1. Double-click on the private folder.
2. Right click on the file you would like to share.
3. Choose Drop Box
4. Click "Copy Public Link"
You've now just created a hyperlink to the file. Within an email message or another document, right-click and choose Paste - here is a direct link to that file.
If the file is in a private folder you will have to share the entire Folder with the other person. This person will get an invite via email and has to login or Sign up with Dropbox to access it.
If you don't want to force the other person to Sign up you will have to put it in your Public folder and share its public link with the person.