For everyone who is giving this a low rating because it won't load in Firefox: Duck Duck Go Privacy Essentials isn't working with Firefox right now because extensions were automatically disabled with Firefox's latest update. It isn't the fault of this extension, but the fault of Mozilla (Firefox's parent) to foresee that their update would break the ability to use extension such as this one. According to Firefox, they are "working on a fix" to enable extensions again.
So please don't punish Duck Duck Go Privacy Essentials (a great extension) for something that Firefox did. Ratings are for how well an extension does what is says it will dom ease of use, etc.; problems downloading or installing (which can sometimes be PICNIC issues) should not be given low ratings, as there can be external causes for these issues. If you download this after Firefox fixes what it broke, it should work again, and work well.