So I just had an interesting experience. I played a game with Mountebank, Stables and Lighthouse. I bought some Stables, with the idea that it would put the coppers flooding my deck to good use. But I also bought Lighthouse, and it did such a good job of blocking my opponents Mountebank that I found myself drawing the Stables in the endgame with no treasure (the rest of my deck was based on Nobles-Crossroad).
I thought that it was interesting because the two "counters" to Mountebank actually ended up (slightly) conflicting with each other, which raises the question: faced with two counters to a powerful attack, when should one double up and when should one stick with the better one? In this case the engine I built (and the fact that I got to open Mountebank when my opponent didn't) led me to an easy victory anyway, but it's easily conceivable that two counters might conflict enough that a player who goes overboard and tries to do both ends up doing more harm to themselves than good.
