First, I am sure your comment about language selection was personal. Facebook in large part stands on PHP; does that mean PHP is better than perl?
Second, I am not sure about their future. It looks like its a temporary spark after all the omg-goverment-tracks-my-searches paranoia.
The fact is, if the large organisations such as Google or Microsoft could not admit on the record to participation in PRISM, what makes you think Duck will? Further, if PRISM is real and if large organisations such as Google or Microsoft could not say "no", what makes you think Duck will have an option for a different fate? Lastly, if there is no trucking by gov of your searches, then there is not much different in using Google versus Duck for someone who has been using Google for years and just temporarily switched to Duck.