You can probably make a good guess based on appearance (clothes, race, gender, general appearance) + their location (which if you are looking at them in person,

You can probably make a good guess based on appearance (clothes, race, gender, general appearance) + their location (which if you are looking at them in person, you know). You are right, you can be wrong, but it'd be worth testing, as my gut feel is you'd get more right, than wrong.