DDG is a great success story, I wish the whole team the best.
I wonder how an exit will play out though. A big factor with DDG is user trust - that seems to limit the list potential buyers to the few that could credibly maintain that trust.
Then there is the IPO route, but that has it's own challenges. You could argue that up until now DDG has had no competition because Google doesn't think it's worth raising its hand to swat a fly. But there is no flying under the radar after an IPO. What if Google promoted a new "no track" feature which matched DDGs benefits without having to do dumb things like append query arguments, modify location, and run plugins?
You might say Google would never give up this much tracking control, but there are two caveats. First, if it's just an option buried in settings there will be limited uptake yet DDG's ability to claim differentiation would be nullified. Secondly, as DDG itself says, search can still be a great business without having to track people.
If I were lucky enough to be in DDGs position I would push for a Microsoft acquisition. MS has kept enough promises in recent years that they just may be able provide DDG users enough guarantees to maintain the trust. People have mentioned Apple but that seems like a lower probability for a variety of reasons. An MS deal would avoid the massive hassle of an IPO and enough resources to chip away at Google indefinitely without being pressured into short term decisions.
For now I'm just glad DDG is here trying to do some good.