Although I do have a few major complaints about the TSA, I'll have to chime in with regards to the one-way issue.
IIRC, CAPPS (Computer Assisted Passenger Profiling(?) and Screening) is the computer system that flagged you. CAPPS has been around for quite a while! I remember my first red flag was in 1999. Back then, your checked luggage was subjected to additional inspection.
Today, if you're flagged by CAPPS, you're subjected to the additional screening by the TSA. For sure, that means more searching as the security checkpoint, as I have experienced. IMHO, flagging should warn the TSA to examine checked baggage more carefully, either by doing a manual inspection (with the pax present of course

) and/or having the TSA closely examine the images of the baggage from the EDS machine.
Note that the flagging is a FUNCTION of how your ticket was purchased, the type of ticket, your history, your destination, citizenship, and some other stuff. (I wonder if the cost of the airline ticket is also factored in? Paying $85 cash for DTW-ORD one-way is fine but $1200 cash for a trans-con is bound to raise eyebrows.)
With regards to the cash issue, it's a red flag because with such a large purchase, it's quite likely someone's trying to hide a paper trail for whatever reason.
Some anecdotes:
* My father and I traveling to Manila round-trip together: both flagged. The checkin agent said that it was mostly likely because we were flying to Manila.
* My father and I traveling to LGW round-trip together: one flagged. My guess is that one of us was a foreign national.
* Traveling alone one-way to BKK (separate return ticket). The check-in agent jokingly said because I asked.

* My mother going to MNL various times round-trip and one-way: never flagged!
While I haven't bought gift cards from AMEX, one would guess that they'd ask for some ID and some other identifying information when buying a gift card. From AMEX's point of view, they wouldn't want to take the that great risk of someone buying a $500 gift card with counterfeit money! Hence asking for identifying information and associating it with the inbound cash would be logical.
To end, remember that many travelers just buy round-trip tickets. The majority of travelers are not as savvy (or crazy) as us FT'ers.
- Pat
[This message has been edited by Wiirachay (edited 04-28-2003).]