Thanks to bookshelves of doom for the link to Linda Sue Park's journal entry regarding her experience as a judge for the National Book Award for Young People's Literature. Park and the other judges read 280 submissions. She says the first cut down to 50 books wasn't very difficult. One of the two major faults, in her opinion was "YA novels with weak story lines and protagonists whose whiny voices were indistinct from one another (LOTS of those)."
I didn't read the 280 books Park read, but generally speaking, I think she has a very valid point.