I have been playing around with the SF zimlet and noticed that I am able to drag and drop emails and they will create entries at the account level, but it doesn't seem to give me the option to create the note at the contact level.
Running 4.5.1 GA if that matters.
- Edit -
I should add, that the contacts I am trying to add notes to exist in SalesForce. I grabbed the latest sforce.js from SVN, undeployed the existing zimlet, did a tomcat restart and then deployed the new version (again tomcat restart) but doesn't appear to make a difference.