Here is Bob Sturm's thoughtful take on it in Why Blog Research ?. Go read it, I'll wait....... Using the blog as a personal database is the reason I link directly to the papers and the people writing them and it is also the reason I share my real time experiments. A side effect of this is that Bob and David's name now show up on the first page of Google when searching for their names. In the end, it is a huge time saver for all of us (notwithstanding the inept search capability Google provides to the blog), however I recently read another good summary of a reason in Social media in science by John Hawks:
Science is a realm in which many highly motivated and smart people are competing for a limited number of jobs. There are many ways to put your work forward, and blogging can be one of them. I never discount that the biggest factor is luck. But 90 percent of luck is standing in the right place at the right time. The beauty of a blog is that it's standing there waiting all the time for the right person to look.
I see this all the time in the counters logs, and I am always astonished at how specific threads are being revisited many years after they were written. Unlike most other science blogs, Nuit Blanche features unpublished works from a highly competitive community. The peer review shows up in the comment section or by email directly to me or the authors. Yes, forget the social media blablah...what you are slowly witnessing is Science in the making. The blog is a sure way to show that your work will sustain the test of time.
If like others you are considering blogging, you might want to read "You aren't blogging yet?" by Bora Zivkovic and Jonathan Eisen.