I kind of share Stephen Downes’ response to Why You Should Write Daily : zenhabits.
I don’t know that everyone “should” do it, but I do think that formulating and expressing opinions regularly (on topics that may not be part of one’s working life) is a useful exercise for most of us. Not having an audience, I don’t really have the option to persuade anyone, so for me it’s more about clarification and reinforcement of my own thoughts and ideas – and protection against the fear that I will forget them.