Until recently blogs and blog posts have not been accepted as legitimate references in scientific writings. This state of affairs is seemingly about to change, however. The 2nd edition of the authoritative Citing Medicine: The National Library of Medicine Style Guide for Authors, Editors and Publishers (2007) includes a new section (26C) with detailed instructions for how blogs and blog posts are best cited in scientific publications.
Okay, we are still a step away from peer-review of blog posts, but the mere fact that the NLM Style Guide now includes rules for blogs and blog posts is a step in the right direction. We may see big changes in scientific publishing practices in the years to come.
(thanks to medgadget for the tip)