2 Billion add-ons have been downloaded for Firefox

"Mozilla is celebrating another significant milestone for its flagship Firefox browser – two billion downloaded add-ons.
In an announcement on its rockyourfirefox web site, the company thanked its developers and loyal users, and talked up the customisation features of the browser.
“[This] feat was made possible by the huge community of people like you who use Firefox add-ons as well as the thousands of developers who make the add-ons you use,” wrote Julie Shin Choi, a Mozilla marketing executive.
“Over the years, we remained dedicated to building features and products that make Firefox the world’s most customisable web browser for consumers and developers."
Mozilla passed the one billion mark in November 2008 and at that time predicted that it would take around three years to double that number. However, it beat that estimate with ease, and Choi predicted that another major milestone would be reached soon."
Source: V3, 2nd July 2010