The face belonging to hand delivery can be easily recognized due to billions of photos available online and the software capable of facial recognition.
Even worse, when hand delivery carries an Android device, their whereabouts are traceable. If they leave device at home and it is deviation from routine, it is easily flagged.
A software using social diagram can predict whereabouts of each social diagram member at any time.
One can be smart, but it's the sum of stupid contacts that counts.
Facial photo recognition has never been successful in application. They want it to be, they crave it to be, but it just never pans out.
And it’s not just an Android device, but all cellphones now have GPS location detection, but that is moot, because if you carry a cellphone, why are you hand delivering a written message to avoid electronic interception? The government even wants to integrate GPS into all automobiles, but has not yet pulled that one off.
And then, on your person there are probably several RFID tags, and when you pass near an RFID reader, you give off a unique signature for that vicinity with even a single tag. Who else in the area is wearing your brand of shoes, and your brand of pants, etc.?
But your last reference was to data mining. A brilliant idea used by both law enforcement and intelligence, it is still dependent on a lack of GIGO, garbage in, garbage out. Even if it established some contacts, it still has no clue as to message content.