Stringer explaining elasticity of demand in the copy shop is one of my all-time favorite scenes in television.
Stringer talking about inferior product in an aggressive marketplace to his teacher, talking about WorldCom, then rebranding... just brilliant.
My favorite part of the series is when String realizes he's been conned by Clay Davis, and tries to put a hit out on him. Avon intervenes and scolds String, saying "what I tell you about playin' them fuckin' away games?" Avon (and later, Marlo) understood that they could never go legit, because going legit is just another unfair game with a different set of rules.
The only character that escaped their fate was Bubbles.
The Wire definitely took attention to detail seriously.