If something "floods the zone with shit," it needs S amount of shit to cause a flood. But too much will eventually make the scam ineffectual. Widespread public distrust for the scam is (S+X)/time where X is the extra amount of shit beyond the minimum needed. Time is a global variable constrained by the rate at which people get burned or otherwise catch on to all other scams of the same variety. If we imagine that time-to-distrust shrinks with each new iteration of shit, then X the amount of excessive shit needed to trigger distrust should decrease over time.
The longer term problem is the externality where nothing is trusted, and the whole zone is destroyed. When that zone was "what someone wrote down that Socrates might have said," or "Protocols of the Elders of Zion," or "emails from unknown senders," that was one thing. A new baseline could be set for 'S'. When it's all writing, all art, all music and all commentary on those things, it seems catastrophic. The whole cave is flooded with shit.