What is clever about BA is the split into 'preferred' bloggers (who get on the home page) and the others. He can therefore monetise all of them without actually having to pollute his home page with some of the nonsense - although there are a couple of exceptions I would push down to the second level!

And even this is a win-win for the second-tier bloggers, because Randy's advertising (for US eyeballs) pays far more than AdSense, even after his 50% cut.