Ezra Klein, founder of The Washington Post's Wonkblog policy website, is planning to leave the Post, according to a report in Friday's The New York Times. The Times says the Post's new owner, Amazon founder Jeff Bezos, and the Post's publisher turned down Klein's request for a dollar amount in "eight figures" to launch a new explanatory journalism venture. It's a boom time for so-called "content verticals" among news operations, with new projects being launched by the Times, The Wall Street Journal and ESPN, among others.