I've talked with many scientists who like the idea of blogging but insist there just isn't any time to do it. To them I ask: how important is publicizing your work?
The honest ones admit that publicity is an essential element of a successful scientific career.
Scientists everywhere are turning away from old-guard information locating services such as Chemical Abstracts Service and toward general-purpose search engines like Google. These ubiquitous new services don't care about your journal's impact factor, it's "prestige", or whatever other factor it's being sold to its contributors on. They just care about the relevance of your content.
The process of building a pagerank that leads to your online content landing in the top three results for keyword searches takes time - and focus.
If you're sitting on the fence about starting an online summary of your research or research area (don't call it a blog if you don't want to), how much valuable time have you already wasted by not starting?