the one about the Niagara falls reminded me of this one: "Les cons, ça ose tout. C'est même à ça qu'on les reconnaît." (Michel Audiard) roughly translated: "Morrons dare everything. That's how you recognize them."

I would just like to point out that this paper: http://www.blackwell-synergy.com/doi/abs/10.1111/j.0956-7976.2005.01576.x titled 'believe it or not' claims to refute the strongest of Gilbert's ideas (and rightly so in my view)