On page 91 in the novel, while the narrator, Marcus was in the Turkish Coffee shop, he was dumbfounded by the idea that based on the new Patriot act, people could track his purchases on his debit card. He posed the rhetorical question to the reader, "You think it's no big deal maybe? What's the problem with the government knowing when you buy coffee?" This is essence to me sums up the idea of privacy vs. security, because it shows how when taken to far, surveillance becomes utterly useless. There is no good that can come out of the fact that the government knows when you buy coffee. Under no circumstances would that ever become relevant in figuring out who terrorists and criminals are. Furthermore, even if it somehow contributed in the most minute way to a terrorist prediction algorithm, someone could just pay cash and get away with it anyway.
Anyone who is trying to plan some sort of nefarious attack is probably going to take the time to figure out what the government is tracking. For example, if the government tracks bank transactions worth more than 10,000 dollars, then a halfway smart criminal would make 20 small transactions worth 500$ each, and the only people that would get flagged would be innocent. If the government is tracking debit card purchases, then a criminal will just use cash. In the end, all this will do is lead to violations of the Bill of Rights and waste a huge amount of money creating a haystack with no needles in it. This is why this particular section in the book stood out to me.