As they go about their daily lives, many Pasadena residents we spoke with, like the rest of us, frequent locations whose populations for one reason or another could be vulnerable — because they attend mosques or synagogues or work at secure facilities, like NASA’s Jet Propulsion Laboratory. We plucked one scientist at the lab out of the data, and when we tracked him down in real life and explained how we did it, he was alarmed. “Somebody who might want to get some information from [the lab] for instance, they might target me,” the scientist told us. “This will be a treasure trove for any spying agency, I would presume.” He asked that we preserve his anonymity in this story.