The problem with that type of indicator is that it will target the same people again and again. An X-ray scan is safe enough to be used in routine medical visi

The problem with that type of indicator is that it will target the same people again and again. An X-ray scan is safe enough to be used in routine medical visits, yet the technician must step out of the room due to dosage effects; so too the effects of even well-regulated police attention are cumulative. (Part of this is probabilistic: if every encounter has an x% chance to go badly...) And that's true even if the indicator objectively performs relatively well, as long as there are innocent people affected. To go back to the current topic, banning all connections from certain countries is an effective way to cut down on fraud without decreasing sales too much; but that still screws over legitimate users from those countries.