I think long term Google will benefit from their actual changes vs. what DDG and Blekko have done, in 2 years when the sites they've banned or selected get better or turn to shit they'll have to rework for that, Google won't. I guess DDG and Blekko are gambling on the fickle nature of "tech" people, but they'll get bitten in the ass by it when the sites they've chosen change and they lose users because suddenly they suck and Google will be there with their proper ranking which can adapt to sites shutting down.

Also the idea that there are people "curating" the way my search works is... unsettling I guess, they're deciding based on arbitrary criteria whether or not they think a user wants a site. What if I like the content DM produce?