The obvious reason for spam of any kind (emails, texts, phone calls, unsolicited mail) is that it is profitable. Thus spam must raise the probability that its target buys or otherwise complies with the spammer’s wishes, e.g. leaves a review. To deter spam, the incentive for it must be reversed – the targeted people should not give in to spammers, but do the opposite (not buy, not leave a review when receiving a „reminder”). I try to follow this strategy. If I remember that a business spammed me, then I try to boycott it, unless it is by far the best option (usually not, spammers are typically shady businesses and bottom-feeders).

Incentives are created by the difference in payoffs, not their level. Thus to deter spam, the buying probability should be lower for a spamming business than for a non-spamming competitor. To create this payoff difference for non-monetary actions, e.g. reviewinig, I leave a review with positive probability when not asked to do so, but certainly avoid reviewing when spammed with reminders.

If the whole society followed the strategy of boycotting spammers, then one possible concern is that spammers would start to use reverse psychology. They would spam in the name of their competitors to make them look like spammers. If customers start boycotting the competitors as a result, then demand shifts to the spammer, which is profitable.

The reverse psychology is unlikely to become a serious problem, because there are typically many competitors and the spammer would have to make most of them look bad to increase its demand significantly. Also, the law usually punishes the use of a fake name more harshly than unsolicited contacting. The competitors whose reputation is tarnished by spam under their name have a stronger incentive to sue its source than consumers just annoyed by the spam.