A big differencee between our 30040 and a gigantic follow list is that: 
the index items aren't meant to repeat (you don't list the same chapter 15 times)
the list has a natural hierarchy, so that you can split it into cascading sections (the Gospels contain Matthew, Mark, Luke and John).

A follow list has no inherent hierarchy (Bob is not a higher-level person containing Susan, Tracey, and Steven).