that does not explain why so many good forum sites have been vanished? They had good user response too and have been well known and established, trusted sites ( in this case i mean coding sites ).
I've seen that also. I'd say it's a weakness in the current state of the algo - but I can confirm tjhat not every forum is having trouble. Nevertheless, ever since Panda 1.0, many forums went from doing really well to having troubles.
Now a search gives my some stupid blog sites and sites that do scratch the topic but will not give an answer? Collateral damage? Or does Google really think they can compete with this scrapped and childish knowledge base?
I'd say that's collateral damage - a weakness in the current state of Google's algorithm. Yes, it probably has something to do with hoping to return "the" answer, eventually through the knowledge base. But clearly they aren't there yet. On TV right now, I see Google advertising the "one answer" mode on mobile search. Mobile is also a very high priority for Google. They feel (and so do I} that mobile usage will rapidly become the majority of traffic.