If you are an author, you must use social media and a blog or website to build your brand. If you want to connect with your network, these tools help with the connections.
Blogs help you show off or demonstrate your knowledge about your occupation and industry. You can share your insights there, update people on trends and events, and build your professional network.
Of course, if your image of yourself is different than who you are, you might need some help figuring out who your network thinks you are.
The answers to what to blog, why, when, and if you should blog depend on the audience and the blogger.