I just spent 15 days in Japan (especially Tokyo except 3 days).
I streetpassed more than 800 times (for the streetpass mii game) . Puzzles are finished.
You don't understand, even at places where there are just 2-3 people which passed near you, the green light is on.
But the most important thing that I noted there is that a lot of people disabled the streetpass mii game to just have their streetpass for other games (Animal crossing, nsmb, kirby, bravely default, etc etc...). If they had activated the mii game, i think that the 800 would rise until 1500 easily.
By example, went to a bic camera store in ikebukuro. After 5 minutes, I open my 3ds and
- Mii plaza 7/10 and Animal Crossing was already at 20/20 !! Just crazy.
With that, I had the gold medal in ANimal Crossing (meet 1000 people by streetpassing)