On Mozilla's Add-ons site (known as AMO), all external links are directed through:
As a random example, see the link in the Description section of this page:
(Similar links are found for the Add-on home page and Support site links on that same page, as well as the link to http://weather.com in the Features section.)
What is the purpose of this redirection?
Is it intended to increase security? If so, how?
Or is it a tracking mechanism?