How many consumer transactions do you envision that are $10,000 cash and over? I can't think of a reason to do one......I guess I must be running in the wrong circles. I think your fear of a HUGE DATABASE is unwarranted.
I do know someone who paid cash for a real estate transaction once....and my assumption at the time was that it was unreported income. Now I am not the IRS...but what would you assume in that situation?
Also, you seem to believe the terrorists did not deal in large sums of money. Atta, one of the terrorists pilots, wired money out of the US the week before 9/11. At one point, he tried to buy an airplane....they had lots of cash.