Right now it seems they're still growing really fast. What if tomorrow it's not the case anymore? What if their userbase reaches a plateau? Will they really still be morally strong enough to commit to user privacy or will they slowly start to give in more and more in order to increase their revenue? Does "do no evil" ring a bell?

On the other hand if they get money from the users themselves then the incentives are different, they might try to get more money by offering new services and they probably won't risk doing that that'll piss off their paying users.

Maybe I'm too cynical but in my mind even if ddg's intentions are pure now eventually they'll get bought or something and someone, some day will want to cash in. And for a free service cashing in means selling the userbase to the highest bidder.

But maybe I'm a bit naive, I guess that would still be possible even with paying users but I think the risk would be greater for them.