The genius part of all that is like I said, we all happened to have our 3DSes on us. Prior to the 3DS era, I had occasionally made plans ahead of time with another person to bring our original DS systems with us for a trip, explicitly for playing some Kart, but that was the exception rather than the rule, as we couldn't always be relied on to carry them. But StreetPass—and the inclusion of the StreetPass Mii Plaza (and its associated activities)—has added a reason for most owners to keep the things on their persons, I think, which made this situation not only possible, but almost a resignation: of course we have our 3DSes with us, it would be weirder to have left them at home, gobbling up no tags, the ironically not-rolling-stones gathering no moss. It's a genius move by Nintendo, really, and I'm convinced there's no way it was accidental.
Nintendo wasn't just guessing when they added an element to the 3DS that was lifted almost directly from the new age of "social gaming." Keep players coming back each day for something little but rewarding. Tags, step counts, the activity log... the part of the equation that Nintendo Nintendo-ly chose to omit was the part where the player gets so addicted to those little rewards that they start kicking out real money to get more of them, ala Zynga and everyone else now. Or maybe I should say that it wasn't omitted, but transformed—Nintendo is interested in the currency which is your interest, your perpetual personal investment in the system. In a modern era where everything competes for your attention first and your money second, Nintendo is going after what's the most valuable—interest, attention. The longer that the system remains continuously relevant to you, the more likely you are to continue to pursue new software to play on it, the more likely you are to receive SpotPass notifications about upcoming titles, the more likely you are to become informed about what's new and what's popular by seeing the games pop up in the "most recently played" windows of people you tag through the Plaza. And consequently the more inclined you are to go on ahead and buy something, only instead of ninety-nine cents for Cut the Rope or a buck or two in energy credits for Donkville, it's five bucks for a back-catalog Virtual Console game, ten bucks for an eShop title, forty bucks for the new Mario, and hell you can get them right there digitally without even going to a store. People sometimes piss and moan about the prices being so much more than this other crap, but then they buy the Nintendo games anyway, because Nintendo has sensibly taken the bold step—which is ironically considered to be bizarre these days—of ascribing actual value to the things they create. And people buy them, because they're worth it.
This philosophy of maintaining attention over time permeates the entire design of StreetPass Mii Plaza, if you look a little closer at it than usual. You can only accrue ten coins a day, to prevent you from gaining too much progress at a time and "using up" all the rewards. You can only hold ten StreetPass tags at a time for the Plaza as well, for much the same reason—to limit your progress through Find Mii. Find Mii had its dark room, a bottleneck that can last for days even if you're using all your coins hiring wandering heroes.
It was no surprise they pushed out the second set of puzzles and the huge Find Mii 2 update with its accomplishment system when they did—it wasn't long after the avid, frequently-tagging Japanese 3DS owners had finished maxing out their puzzles and completed Find Mii and its secret quest. With Find Mii 2, they added the new feature of recruiting old heroes to get past those roadblocks, but they cost more, and you often need two of them now, and there are more roadblock rooms and shields to slow you down. Acquiring all the hats takes multiple playthroughs, and the last four levels in the special quest progression can take dozens and dozens of heroes—all things designed to keep you coming back on a daily basis for those little rewards, as long as possible.
As many players are encroaching on getting the last few hats and most people in tag-heavy areas have long since finished all the puzzles, I wouldn't be surprised to see Nintendo take it a step further and get Find Mii 3 out before much longer, to keep that stream of content going. The more there is to chip away at, the longer the gamers will keep those things on them. And in a world where mobile phones fight for virtually all attention most of the time, it's critical for Nintendo to keep as much of that valuable attention as they can. And that's just the StreetPass implementation in the Plaza. The honeypot is substantially sweetened by the tags in other games that keep you coming back, much like my coin rush tags in New Super Mario Bros. 2 have been doing. Get the tags, beat the scores, push forward to the million coin goal. It doesn't even matter what you get for a million, just that it's there, and it keeps me coming back.
For as much as people like to disparage Nintendo for being "archaic" and behind the times with everything from the hardware in their boxes to their Internet strategy, the things the 3DS is doing with "social networking" are seriously forward-thinking. I am sure people fail to even regard StreetPass as social networking because it so little resembles the implementations that we're used to, which are more and more based these days on voluntarily interacting and sharing with your actual, real-life friends, using your real name, retweeting the content of others, posting links from around the web. Instead what we get with StreetPass is a voluntary—but automatic—form of positional networking, where the results and the pieces of information you're sharing are all literally based on your physical proximity to others, your schedule, your routine, what games you're playing. Internet companies have been attempting targeted advertising since the days when people thought it was funny that their computer needed something called "cookies," and Nintendo's doing it in a way now that isn't necessarily superior or inferior but parallel, a new approach. If there's anything that I think we could have come to expect from them by now, it's sliding things in under our noses in their own Nintendolian ways, without us really even noticing what they're doing.
In a way, I guess I shouldn't have felt it so surprising that the four of us, headed out for burritos after work, happened to have our 3DSes with us. To me, there was a more interesting question. How many of these other StreetPass tags I got between the escalator and the seat originated from different 3DS systems that are on the same car with me, tucked into a bag? And what game were they playing last?