Two very important points in this: If you want your blog to contribute to your bottom line, you need visitors to "perform some other action." Also, Mack is letting his social graph curate the high-volume blogs for him.
I always say that leads should be treated like customers because they have bought something with their contact information or attention. Here's a service that actually lets your visitors pay by sending a tweet to their audience. This may let some of your content go viral.
The leaders in the Facebook fan page world should have some great ideas for the rest of us, but don't take them at "face" value. We don't know what will work for us without testing. Plus, these are all major brands, an advantage most businesses don't enjoy.