Never got into streetpass with the 3DS. Seemed like a waste of what was already pretty limited battery life. I typically kept all that turned off. I did end up going to a pokemon tournament in Atlanta with my bro and my oldest son (they played, I was mainly there as the driver) fairly early in the 3DS's life.... and that was bonkers crazy for streetpass. I can see why it might have been pretty popular in Japan and other areas with a dense population.
I would just like to say, for the record, that after about 10 hours (or less), Miitopia 3DS is the most boring thing ever.
Glad I passed on it. It looked pretty boring in the videos I watched when it was announced.