"A 20 year-old college junior with little in the way of reporting skills to offer simply couldn't break into the blogosphere these days," writes Matt. "Thus, I think you'll find that folks like me, Ezra Klein, Julian Sanchez, etc. are blazing a trail that nobody will follow."
Oh, I don't know about that. I was just involved in the hiring process for a writing position, and we not only searched out online experience, we demanded sample blog posts. And I doubt we're particularly unique. Given that every major pundit-type magazine now has a blog, you'll probably see some familiarity with the form become a prerequisite, if not necessarily the primary credential. Magazines need constant content, and they particularly need young writers willing to provide it, as older writers remain, by and large, reluctant and infrequent bloggers (there are obvious exceptions to this rule). The effect of this need for blogging among new hires, however, is fairly immense.
It used to be very hard for a young writer to make a name. The question wasn't one of talent, or brains, or style, but of simple opportunity: A traditional magazine has X number of pages a year, which are split between many authors and topics. A new hire gets neither the best stories nor the finest assignments. Her writing is edited and reshaped, homogenized into the voice of the magazine. Given these constraints, it's not impossible that she'll break through, but it's unlikely.