I always laugh when I read those questions - they are hillarious... things like "Have you ever, or are you planning to, take a child from the custody of a US citizen, that has been awarded custody", or all the drug related questions... I mean, even IF
I were planning just that, how dumb would I have to be to answer YES to any of those questions?
I especially like the "if you answered YES to any of the above questions, please consult a US Embassy before commencing your travels" (or something like that) - considering that a lot of people, at least before the current changes if visa-regulations, received that card somewhere above New Foundland or even the New England states of the US...
That always made me wonder: is there a US Embassy somewhere between the arrival gate and the immigration counter?
But, in all honesty, people really should take more care when planning trips, not just to the US: even in cases where I'm certain that I don't need a visa, I'll always double-check: better be safe than sorry!
And I think these questions also have to do with the fact that, should you be caught doing something illegal in the US, especially something that you answered "NO" to on that form, they'll be able to deport you even faster, since you lied while entering the country.