I have a three Streetpass Communities within a drive away (one close, two far - but not too far) from one another. One of them is extremely active. The other two go active during spring and summer.
There's also one hidden Streetpass group near me - they rarely post when they're meeting up publicly and mostly stick to sharing each other's phone numbers and friend codes when they meet up and plan meetings through texts or SwapNote. They meet almost as often as the largest Streetpass group, but just never post it - so you have to find them...
So in all I have 4 Streetpass groups near me.
Getting a Streetpass during the weekends is easy - and if one wanted a LOT of Streetpasses, they just have to run into one of the groups during their weekend meet. Heck, even if we didn't have them, we're near a convention center which almost guarantees hundreds of Streetpasses at any game/anime/comic event!
I don't have as much Streetpasses as some people have in my area (and I lost about 150 of them when I got my 3DS returned from the repair shop), but I do have a lot.
That said: All my puzzles are complete and I'm only missing a few hats in Find Mii.
And if I get a new puzzle? I just have to wait a week or two for a weekend burst of new pink pieces from passersby.
Sounds like I'm bragging? ...only half.
The other half is being disappointed in not having enough Streetpass things to look forward to.
I can't afford anyone's gems in Kid Icarus Uprising (and it'd be such a waste to just crush them), I don't play Kingdom Hearts, I don't really care for challenging people's records in Mario Kart or NSMB2, without much customization the fights in Dead or Alive Dimensions are feeling stale after a while, it's been forever since I've gotten an awesome creature in Freakyforms (most just make a random mess of... ew), the figurine battle in SSFIV lost its charm A LONG TIME AGO (though I still check it), no one sends Streetpass SwapNotes, I haven't gotten Resident Evil Revelations yet (it keeps getting pushed back on my backlog), no one plays Rhythm Thief, aand... and... I think that's about it.
It would've been lovely if there was Streetpass features for MGS3D, PushMo, Dillon's Rolling Western, or even just a brand new game that doesn't just have competitive score/ghost/timer-record Streetpass functions... I like either competing against an avatar or trading items!
The only game I have to look forward to for this stuff is Animal Crossing....
When you have tons of Streetpasses from strangers, you then stop getting excited for the Mii Plaza stuff and just wish you could do more for the games you actually own...... You just wonder "Shoot, it would've been nice if I got something for this game."
And we all know how much Pokemon Black/White 2 could've benefited from Streetpass functions (without having to leave the game on)....
(And leaving my 3DS on and traveling isn't a problem. I have a 3rd party battery that lasts DAYS when it's shut, and 10 hours when it's open (with 3D and sound at max))