It has been widely speculated that the customs form that they pass out on the airplane en route to the USA is not about stopping bad guys but about getting them to lie on official paperwork so that there is a documented crime to cite as a reason to deport/jail them.
The ones here in Uruguay and especially Argentina are mostly concerned about illegally entering or withdrawing cash (US Dollars mostly).
You have to declare cash above a certain amount, and I believe excess cash can be confiscated.
There are also other questions (for example: if you're bringing animal products - we had very damaging outbreaks of foot and mouth disease, the mad cow scare, etc)
The I-94 form asks such questions as "have you ever been or are you now involved in espionage or sabotage; or in terrorist activities; or genocide; or between 1933 and 1945 were involved, in any way, in persecutions associated with Nazi Germany or its allies", "have you... procured or attempted to procure a visa or entry into the U.S. by fraud or misrepresentation?", and "are you seeking entry to engage in criminal activities?"
Yes, I know. I'm fairly confident it's the form
tedunangst referred to, and to travellers, the distinction is mostly academic, since they're both handed in at customs.
