What other search engine is there? There's Microsoft and Google with deep pockets. Does DuckDuckGo have fat stacks of cash sitting around for some reason? How bad would it be for Mozilla to take Facebook funding? Would we really stand for it if Moz got funding from Baidu or Yandex?
I mean, insofar as we stand for things that the Mozilla foundation does now, which are mostly terrible and stupid.
So probably Facebook then.