For something like Critical Realism, blogging raises awareness by taking something abstract, and instead of allowing it to collect dust, it becomes manifest subjectively through your own words. It becomes lived instead of just thought about. Also, as Michael Berube wrote,
To popularize the more controversial academic inquiries of the past twenty years… is thus only to take seriously the claims of our scholarship on the lived subjectivities of ordinary people.While I dislike language like "ordinary people," as though scholars were prophets, the idea is that a good litmus test for a belief is whether or not you are bold enough to share it.
In the past, there may have been better venues for sharing ideas, such as opinion columns, etc. Unfortunately, printed mass media is a dying animal. Scholarly books, articles, and conferences certainly have an important role in that they are peer-reviewed and thus legitimized. But relying on the slow gears of academia to promote an idea is like lying under a bee hive and waiting for honey.
Finally, there is an aspect to blogging which is not necessarily evident unless you have participated in writing or commenting on blogs: community. Bloggers are initially quite lonely -- after all, they spend time crafting posts, excitedly publish them, and wait, wondering if anyone is reading. It turns out the best way to build blog readership is to find other blogs and comment on them! Thus blogs become interconnected (literally through hyperlinks), conversation oriented communities.
So if you've never considered blogging before, consider it. If you've written blogging off, reconsider. If you consider it a waste of time, think of all the goofy things you spend your time on otherwise!
How to Set Up a Blog