Your third point really hits home for me. The most useful questions & answers I've ever found on S.O. tend to be locked more often than not. And even if they are slightly off topic, they're much more useful and informative to me during my research than the more common type (e.g. http://www.doxdesk.com/img/updates/20091116-so-large.gif). I understand this isn't the point of S.O. but there's really no resource like it for that kind of research.