Watch some of those border/airport shows and you wouldn't be surprised at $15k. No matter how many times people are told don't do this, you will find bus loads of people who will do it. Same goes for medication (never mind you tell them split the meds up into two or three packets in case there are mishaps (eg, spills and whatnot).... don't put your laptop in checked luggage... don't carry more than $10k on you....

I wouldn't say they're stupid, more they think they know better... this is the kind of advice I give to my relatives, some who travel far more than I do... but they insist on doing it until it happens to them. I'm pretty sure I have that attribute as well, although I don't know exactly for what type of stuff.