This is exactly what ResearchGate aims to be - a social networking platform for scientists and researchers to share papers, ask and answer questions, and find collaborators.
In this interview [1] Ijad Madisch the founder & CEO of ResearchGate envisions ResearchGate to be a home for negative results.
[1] http://www.zmescience.com/other/interviews/qa-with-dr-ijad-m...