[Johnny555]

If they have cameras that can track people via facial recognition, then why would they need to track people via body scans?

If they really wanted to use body scans to track people, they'd arrange the checkpoints so the body scanner is the first place you go after they scan your boarding pass and/or ID. And when questioned about why they rearranged the checkpoints that way they'd just say "TSA security evolves to counter ever changing security threats, and we can't speak specifically about what prompted this reconfiguration." End of story since security theater is not to be questioned.

[lwhalen]

Facial recognition is fragile - a simple prosthetic or three can throw it off. Body recognition (and gait recognition) is less so, mainly because there's relatively MORE of it that would need to be disguised.