Brazil nuts are perhaps best known for floating to the top of a jar of mixed nuts. According to Wikipedia,¹ the reason for the phenomenon is not well understood.
At least in my house, the reason for the phenomenon is quite clear: Brazil nuts float to the top because nobody in my house likes Brazil nuts. When you reach in and grab a handful of nuts, you toss the Brazil nuts back into the jar, which is why they end up on top.
A few months ago, I asked "Does anybody actually like Brazil nuts?" A lot of people agreed with my opinion of them, but there was a notable dissenter: Larry Osterman. There is now a symbiotic relationship between my family and Larry Osterman. Every so often, I will skim off the Brazil nuts and bring them to Larry. Both sides win: We get rid of the annoying Brazil nuts, and Larry gets a small bag of Brazil nuts.
¹ Translation: I could just as well be making this up.