I like the DuckDuckGo search engine and what the DuckDuckGo team tries to do, but this extension blocks the proper behaviour of some WEB sites under FireFox for no good reason. Typical example is easyjet's web site (easyjet.com) where various links stop working once the DuckDuckGo extension ins installed.
So, I'd say "nice try, but no thanks".
Keep the good work on the seach engine, but either fix the extension or drop it.