Well, "Google" rolls off the tongue much easier than "Duck Duck Go". "Duck Duck Go" is also hard to "verb", as it were. I don't have a problem with the mentioned silliness of the name, I just think it's too long and hard to say/write.
Rebranding is not too difficult if you don't get much traffic from organic search. It's a simple redirect and a notice on the page.
It's also not too difficult when you're small but gets more costly as time goes on. If DDG succeeds, the customer base it has now will be something like .00001% of it's users.
The seriousness of DDG is to make damn sure that when someone types in the word 'dog' or some other simple search test, that pointed, relevant results are returned. And for that DDG seems to be getting better at each day.
He's been very upfront about who he is (one man operation) with zero interests in storing personal tracking information (the antithesis of Google).
Before the advent of Twitter, pg would attribute quotes to Tara Ploughman when he wanted to write one-sentence essays. (Since the advent of Twitter, he curiously has stopped writing one-sentence essays.)
Here, I'll invoke "Tara"
"The less confident you are, the more serious you have to act." - Tara Ploughman