1000 True Fans by Kevin Kelly (Recommended by Tim Ferriss during his Tim Ferriss on How to Reinvent Yourself with Blog Marketing interview on Copyblogger):

A creator, such as an artist, musician, photographer, craftsperson, performer, animator, designer, videomaker, or author – in other words, anyone producing works of art – needs to acquire only 1,000 True Fans to make a living.

A True Fan is defined as someone who will purchase anything and everything you produce. They will drive 200 miles to see you sing. They will buy the super deluxe re-issued hi-res box set of your stuff even though they have the low-res version. They have a Google Alert set for your name. They bookmark the eBay page where your out-of-print editions show up. They come to your openings. They have you sign their copies. They buy the t-shirt, and the mug, and the hat. They can’t wait till you issue your next work. They are true fans.

To raise your sales out of the flatline of the long tail you need to connect with your True Fans directly.  Another way to state this is, you need to convert a thousand Lesser Fans into a thousand True Fans.

Read the full article: http://www.kk.org/thetechnium/archives/2008/03/1000_true_fans.php