This is probably nothing to be worried about or whatever, but I've been having some trouble getting Streetpass for Streetpass Mii Plaza.
I remember my friend came over and spent the night for two days, but I only got two Streetpasses from him even though he was there for more then the 72 hours. In my experience, 72 hours would be long enough to get three Streetpasses from the same person.
Also, I went to 4 places that had Streetpass Relay Points, and got Streetpass data from 3 out of the 4 places, but didn't get any data for Streetpass Mii Plaza, even though I got tons of other data for my other games with Streetpass turned on for them.
If it helps you guys, I currently have 9/10 people at my gate in Streetpass Mii Plaza, and the last day I played it on was on January 9th, I believe, so I have no Spotpass Miis at my gate.
I know it's sort of a silly question, but I hope I could get some help, regardless. 