I've gone back to school; or at least, I'm taking one Master's-level course in Media Theory at Concordia University. So I've been reading a fair bit of academic writing. I've come to the conclusion that all academics should blog. Here's why:
1. You need to improve your writing
I have never read such dismally bad writing as that which is prevalent in academia. Not all of it is terrible, but the stuff that is bad is just atrocious. It's wordy, flabby, repetitive, and filled with jargony mumbo-jumbo. I realize that jargon is the very stuff that you work with and to the extent that you need your topic-specific jargon to make a point, then you should use it. But there is a whole other class of general academic mumbo-jumbo that you need to cut out of your writing right now. Go read Orwell's rules, and then Strunk and White, and then we can talk about it again. Hint: utilize=use, militate=block, empower=mumbojumbo. You need lots of practice writing clear, good prose and saying what you mean. Blogging will help you get that practice.
2. Some of your ideas are dumb
The sooner you get called out on bad ideas, the better. Blogging has an almost-immediate feedback loop, and if you write a discipline-specific blog, then your colleagues around the world will read it (if they don't then you are doing something wrong). That means that when you have a dumb idea, you should hear about it quickly, and you can then reconsider. When you have a good idea, you'll hear about it; when you have an incomplete idea, and some others chip in with suggestions, you'll get a better-formed idea. Etcetera.
3. The point of academia is to expand knowledge
If you believe that the reason academics publish is to expand knowledge, then expanding it beyond the few tens or hundreds of your colleagues that read the obscure journals you publish in should be a good thing. Your ideas should matter (if they don't you should try to come up with some better ideas). If they matter then more people should know about them, and right now almost all your ideas are locked up inside the walls of journals, academic conferences, and university quadrangles. Set them free, and the good ideas will spread, be built on by others, and knowledge as a whole will benefit.
4. Blogging expands your readership
Cross-polination of ideas makes for a more healthy intellectual ecosystem, and blogging means that anyone, not just those in your discipline, will be likely to read your stuff. This includes other academics, as well as the rest of us (politicians, policy developers, artists, engineers, designers, writers, thinkers, kids, parents, and on and on). Anyone might have an interest in your work, or nuanced ideas about how it might be improved, or indeed thoughts on how your thoughts might improve their own thinking on a particular (perhaps nominally-unrelated) topic. More readers, from a more varied background, means your ideas will have a bigger impact.
5. Blogging protects and promotes your ideas
By blogging a new idea, you put your stakes in the (cyber)ground, with dates and readership to attest to your claim. When you blog, you've published, meaning people know you have published, and further meaning that a much wider audience - anyone with an Internet connection - can get access to your ideas. Which leads to the next point.
6. Blogging is Reputation
In blogging links are currency: your reputation is made by who links to you and how often. It's a built in, and more-or-less democratic system of reputation as defined by interest. By having your ideas online, the value of your ideas (as reflected by who is interested in them) becomes immediately apparent. The academic/journal system works in similar ways, with Journal references as the currency. So you should be right at home.
7. Linking is better than footnotes
Linking is much better than a footnote. It allows your readers to visit your source material immediately (assuming it too is online), so again is likely to expand knowledge by giving readers direct access to the ideas that underpin your ideas.
8. Journals and blogs can (and should) coexist
Blogs and (online) newspapers exist in a symbiotic relationship: bloggers sift through and refer to newspapers, sending traffic to them. Newspapers now blog, and bloggers write newspaper articles. There is a general sense that blogging can be a bit more free-form, a bit less polished. While newspaper articles are more rigourous and final. Something similar should happen with blogs and journals. If academics blog, they can evolve and develop a series of ideas. When the ideas are clearer and polished, they can move on to be journal articles. But let's get those journals online and free as well. Speaking of which:
9. What have journals done for you lately?
Journals define your reputation, and don't pay anything. That's like blogging. They are exorbitantly expensive, have abusive and restrictive copyright terms, and are not available online to the general public. You can't link to them, and often you can't find them. That's unlike blogging. Journals should all be open access and free online (as newspapers have come to be), and you should tell them that, and choose to publish in open access journals whenever you can. It's good for knowledge, and you are in the knowledge business. You should support whatever is good for knowledge.