probably 3 to 5 years ago

yes

yes, i streetpass people at school

Probably; I have a friend with a 3DS who I think tagged me in Mario Kart a couple days ago

I used to get a lot back when the 3DS was carried around by everyone, now not so much.

Never in my life

all the time back in the day. one of the most fun features nintendo's ever made for sure. you were basically guaranteed to get at least a few green lights in any public area. i miss that era :'-(

many times, many years ago

Yes. my whole family and some of my friends own 3DSs, and I've tagged a few in my home state.