I just found this article from Seed regarding Research Blogging, and specifically the below exchange interesting. All highlighting and emphasis is mine.
What do you look for in a post you select for ResearchBlogging.org’s Editor’s Selections?
SkySkull: I really choose posts by reading them and seeing what catches my eye! Looking over those posts I’ve selected, I would say I choose Editor’s Selections by three criteria: broad interest, technical accessibility, and added value. Broad interest refers to a topic that would be enjoyed by anyone excited by science. Technical accessibility means that the post is written to be accessible, at least in part, to a layperson reading it. A post with added value gives some insight into the topic beyond that stated in the original article, be it historical background, personal reflections, or some other additional context.