<font face="Verdana, Arial, Helvetica, sans-serif" size="2">whenever you specify criteria to reduce the odds of a specific person getting scrutiny, you make it easier for patient and determined terrorists to beat the system.</font>
For instance, Palestinian women are now blowing themselves up at Israeli checkpoints.
cf. "my elderly mother in a wheelchair was given the full treatment, how can they do that does she look like a terrorist!?", which is why truly random screening will never fly. Until an elderly woman blows herself up (or is blown up).
andrew