Going into this, my expectation was that blog popularity and scholarship would have little (or perhaps even a negative) correlation. After all, the skills of a blogger (writing quickly and well, working for short-term results, spending a lot of time reading and digesting others' work) are not necessarily those that a scholar who wants long-term impact needs to have. Plus, there is the time spent on the blog--which does mean less time for research. Remember the Acemoglu response: I am too darn busy writing research papers... And one can certainly be an excellent and popular blogger--providing stimulating commentary on others' work--without having large scholarly output or high impact.
And yet the correlation between how well one does on bloggership and on scholarship turns out to be positive and statistically highly significant. The rank correlation between the two is 0.27, and it is significant at the 99% level of confidence.