Add Ray Dalio to the list of people who write (or blog) everyday.  In his new book, Principles, he talks about his process and the rationale behind it.

In the late 1970s, I began sending my observations about the markets to clients via telex.  The genesis of these Daily Observations was pretty simple.  While our primary business was in managing risk exposures, our clients also called to pick my brain about the markets.  Taking those calls became time-consuming, so I decided it would be more efficient to write down my thoughts every day so others could understand my logic and help improve it.  It was a good discipline since it forced me to research and reflect every day.  It also became a key channel of communication for our business.  Today, almost forty years and ten thousand publications later, our Daily Observations are read, reflected on, and argued about by clients and policymakers around the world.