There's little doubt that honest people, who simply thought they'd found a good deal on the internet would get stung at the airport if AC were to take such an approach, although I suspect that they already would/do anyway if someone came to checkin and they suspected the ticket of being fraudulently issued in anyway.

The biggest question is, how would they know?

If the numbers being thrown around are to be believed, this is big business and some people are making a lot of money from this. Anything that evolves to that stage will be sophisticated. It is commonly suspected that they have automatic bots setup to book tickets the minute they're issued on popular routes (why not, such things exist for concerts, sneaker releases and so on). One has to assume they take precautions not to get caught, i.e. fresh "burner" AP account per ticket etc.

Distinguishing them from regular first-time customers may not be a simple task.