On SEO Ibérica we encourage all employees to have a blog. The reason for this from our side is that we think that blogging is a great fun and great way to learn more about the online world and in our case, especially search engine optimization.
The main advice we give our employees is to blog about topics they like. Otherwise it will be a boring blog experience. Blogging requires energy and commitment and if you write about a subject that you are not especially interested, the blog wont be interesting either.
An important source of new readers to the blog is of course the search engines and to rank high on relevant keywords on relevant search phrases. Just the feeling of reaching more and more readers are in my opinion one of the large advantage of bloging.
If you don’t use blogs, I recommend it highly. But choose the topic carefully. Choose to blog about something close to your heart.