Can I use my blog posts for an academic publication? It is not very clear in the publication guidelines of journals or conferences whether one can post some preliminary data or results online (blog, twitter, facebook, etc.), gather feedback, and then edit and publish such results in a journal or conference publication (but in other fields it has happened with some embarassement).

Can a researcher post a blog-entry, or use twitter, sharing data and results with a journal or conference paper? Would it be considered self-plagiarism?
You'd need to ask the specific journal if they're okay with it.  I suspect many would be, since many other forms of quasi-publication prior to a paper are acceptable.