how do i privatize my Alexa rank ?

[riaz f]

While most sites display a high ranking, a low ranking or a "no rank" in the Alexa toolbar...... Alexa has privatized its rankings (ie: "private" is displayed in the Alexa toolbar.

Why is that "private" display only available to Alexa ?

[G]

Its possible that it has something to do with alex toolbar being spyware. Read the complaints here.
http://www.siteadvisor.com/sites/alexa.com