This sounds a lot like StackExchange site. I understand you're limiting it in scope to only things that are impossible (or difficult) to find on the Web already, but the main problem I see with that is that many (most likely more than half) of users of QA sites didn't do a Google search to start with.
Some of the draw of a QA site is that someone can ask the question and the answer comes to them -- there's nothing to filter out the "easy" questions, or in the case of your idea, the already-answered questions.
Comments
This sounds a lot like StackExchange site. I understand you're limiting it in scope to only things that are impossible (or difficult) to find on the Web already, but the main problem I see with that is that many (most likely more than half) of users of QA sites didn't do a Google search to start with.
Some of the draw of a QA site is that someone can ask the question and the answer comes to them -- there's nothing to filter out the "easy" questions, or in the case of your idea, the already-answered questions.