Interesting responses
Well, let's see ...
In my case I believe that the purchaser will pay the agent through a bank transfer, fairly common here. No 'cash' per-se but he could have taken a wad of cash down to the post office and settled the invoice there. The post-office wouldn't blink an eye at a few thousand being paid over the counter.
In much of the world credit is unusual. What's the credit card penetration rate in Africa, or in India? Mind you I was surprised that the undie-bomber didn't use one of his daddy issued credit cards. Perhaps he was cut off but I'd be surprised if he didn't have plastic (W. Europe resident). And why did he buy a one-way ticket, I'm sure he could have got a RT for the same, or less money. Not to save money (why would he care) but to generate less suspicion.
Yes, I do have a round trip ticket (in Club) and that makes me less risky because ...
APIS? BA has my passport information which I filled in on-line.
So, I guess we can remove these two things from the list of things to look out for ...