Here's the first sentence of Stuart Klawans' review of There Will Be Blood, as printed in the January 28, 2008 issue of The Nation:
By the time the boy lies moaning on the floor, spooned against a father who is helpless to soothe him, the earth has blasted open, fire has whooshed up through an oil derrick and a dozen roustabouts, dwarfed by their handiwork, have raced in all directions across the stony Central California hilltop, trying to contain the immense forces they'd set loose.
The first time you read this, did the main clause's figurative language cause you to ask "wait - is the fire whooshing somehow through [as in "among" or "forcibly separating"] the roustabouts as well?" Cuz it sure did me. Which meant that at first, I was slightly at sea on the question of what "dwarfed" was doing: verb? past participle? Ultimately, of course, it becomes clear that it's the latter, that it modifies "roustabouts," and that the phrase beginning "a dozen roustabouts" is the third in a series of clauses describing what happened "by the time the boy lies moaning..." (the first two being "the earth has blasted open" and "fire has whooshed..."
In a long, complex sentence like this one, what possible justification is there for omitting that comma, which would have gone a long way toward clarifying the sentence's structure?
None that I can think of.