In Side-effects in Medicine Jochen Fromm noted that bacteria that develop resistance to antibacterial drugs are an unintended consequence of the use of those drugs. In A Paradigmatic tax dodge I discussed tax dodges. It strikes me that these two unintended consequences are quite similar. (Of course one of the points of this museum is to note similarities among unintended consequences. So it's not surprising that they are similar.) But in this case, the visible effects seem so different that it is striking how similar the underlying mechanism is.
In both cases, a mechanism is installed in the world. In one case it is anti-bacterial drugs. In the other case it is some tax laws. Both of these are in some sense noxious to some population: bacteria and money maximizers. In both cases, the population evolved mutations that are able to neutralize or otherwise avoid the effects of these noxious mechanisms. So these are both examples of avoidance adaptations.