Its only CASH deposits equalling or exceeding 10k that MIGHT trigger a SAR. Other traceable forms arent that big a deal unless they come from a suspicious source or known tax haven.
The purpose of a SAR is catch money launderers and tax cheats (the terrorist angle is just for public consumption, they use foriegn banks). The most commonly caught tax cheats are small car lot dealers who try to circumvent the SAR by deposting cash into several accounts (usually relatives) at different banks. They get caught when a teller sees a familiar face (the dealers daughter from the last case I read about) bringing the same bag with lets say $3500 cash for Tuesday, $1900 cash Wednesday, $5000 cash Friday, etc.
$10k is just a threshold, but if circumvention might be in play you get SARd. Then the IRS scans all accounts at all banks in your SS, determines the source of the cash (your dads car lot) when you get questioned (lying to Federal authorities is also a crime) and then youre just screwed up the you know where.