Value is created by doing.
It’s easy to forget this. A lot of stuff feels like work—commenting on HN, tweeting, reading about other companies’ funding rounds, grabbing coffee, etc —is not actually work. (If you count that as work, think really hard about the value you’re creating in your job.) These activities can be worthwhile in small doses—it’s important to network and meet interesting people to stay in the flow of ideas—but they are not by themselves how new wealth gets created.
Value gets created when a company does things like build widgets and sell them to customers. As a rough guideline, it’s good to stay in roles where you’re close to the doing.
 I count blogging as a marginal use of time, but the reason I started is because I realized it was important to be good at writing, I was bad at it, and the only way I was going to improve was with lots of practice. And sometimes I meet really interesting founders because of something I wrote.
(1) I started blogging for personal brand, but quickly realized that the goal was unclear (vanity?) and it didn’t justify the time.
(2) Now I blog for practical reasons: (i) My blog posts are excerpts from the most useful articles I’ve read, so publishing a blog post every day forces me to constantly search for best practices. (ii) Selecting the key excerpts forces me to read more carefully. (iii) Tagging the posts produces a library of insights I frequently revisit. In other words, writing the blog makes me a better CEO, irrespective of whether anyone reads it.
(3) The bonus: Other entrepreneurs have told me they find my blog helpful. So it’s a great way of helping others.