I used ChaCha a few times to find out how it works. They (underpaid Americans) use the same search engines as I can use, so that was not of any help to me. For some people that have no clue it’s probably a nice option. I’d rather search for it myself, so that I know I have all there is to find.
The legal position of a human edited search engine might change. I would say that it does not make much sense to lower liability standards in comparison to other publications. If Google gives a link to a madonna mp3 file, Google can defend itself with stating it did not know. If I ask ChaCha, I guess the person helping me would not be allowed to help me, or would she?
My guess at the main reasons why there are some recent attempts to power search in this way, is because to do it the algorithmic way ( which does certainly not exclude a human role in editing) means doing it the same as Google and the other big ones. Human powered search aims for a small piece of a very big pie.