Let's be clear about it: yedda won't surpass yahoo answers in terms of quantity, or Google answers in terms of qualit, as Google answers are paid for.
You won't neither have the same trouble with Yedda, that you may have with Wikipedia, where the information often varies according to political, religious or business wise criteria.
For me, what makes Yedda much more interesting, is that it is not related to any existing Yahoo/Google/Microsoft/EBay compendium. Ie the information is shared there, will not - maybe I'm wrong - by any of these big companies, in order to make money on top of my Web usage. And this makes a great difference.