Augie was familiar with these from movie theaters and the bank where he was currently overdrawn, and understood the purpose: to cram as many people as possible into as small a space as possible.
-- Narrator (Gray Mercedes)

Importance: This quote not only makes reference to the bad financial shape in which Augie finds himself, it also describes the way the people are crammed into a small space, making it easy for the Mercedes Killer to ram a car into the crowd.

I imagine if there was ever a ‘perk’ you wanted to catch, Detective Hodges, it was the man who deliberately drove into the Job Fair crowd at City Center last year, killing eight and wounding so many more. (I must say I exceeded my own wildest expectations.)
-- The Mercedes Killer (written in a letter) (Det.-Ret., Section 3)

Importance: The Mercedes Killer uses the fact that he has not yet been caught by the police to goad Hodges. Brady believes Hodges failed in his career...