I'm not certain "growthful" is a word, more like a neologism. My guess: you know exactly what I mean by it - people who write for an audience become better writers and thinkers as a result. They grow, mentally.
I've held this view for some time without quite articulating it. Now comes along an article on the website Wired.com that spells out this view and supports it. If you write for a blog, or read them with some regularity, I believe you will find the article interesting.
