It's a yes and no from me. Obviously I do it, but I can see how many people don't and why they don't: they have a very busy life outside of work. Very few other professions encourage blogging about work outside your working hours. Tell a car mechanic they should whip together a blog post every week or so. They'll be like "go away, and never come back". Don't get me wrong, all your reasons are 100% valid, but I would argue that only people who genuinely enjoy doing it should do it. For example, it should certainly not be the reason why one engineer gets hired vs another who doesn't blog.