The way that Nintendo has actually chosen to implement the "results" of the mode is actually pretty entertaining. When you first get a StreetPass tag, the person you tagged shows up in your list as a little ? block that you need to click on to "unwrap," much like a present from the eShop. After you do that all you see is the Mii and name of the person you tagged, along with what Pack they challenged. You don't actually get to see how many coins they got until you finish the course yourself, which is kind of a neat dynamic, as you always try to do your best the first time without getting stressed out if you miss one of those x2 flagpole touches or don't do quite as well as you had hoped. After you finish, you get the dramatic reveal, as the rival total is displayed (along with an icon that indicates if the performance was done with the white raccoon suit), followed by yours. The reward for just "doin' your best" that first time is of course all the coins the other guy actually got, regardless of whether you happened to beat their score or not on your first try. If you did a great job, sweet—a nice feature of the mode is that it lets you save your StreetPass record attempts as your own personal bests too. After that first playthrough though, the quest to beat the score is the thrill, and it really can bring out the competitive feeling.
The reward for beating any score is the elusive "crown coin," which instantly adds a thousand smackers to your pile of gold doubloons, and also fills in the circle on that person's record. The game keeps track of your total number of historical StreetPass tags, along with your total victories, so the perfect-record completionists better make sure to beat them all before new tags take the place of their older ones. A nice feature though, in exactly those types of situations, is that you can set any of these people's tags as your "favorite," ensuring that if you find one person's record particularly tough to beat, or come across a tag that features a selection of levels where you can really rack up the coins, it won't get pushed off the screen by future StreetPass tags.
The maximum number of tags at a time for this game is a mercifully large fifteen, enough to completely fill up the in-game coin rush tags screen. I haven't had the opportunity to get any tags that would be "too many," which is to say more than I could hold on that screen considering the favorites I had saved, so I'm not sure what the game would do with those tags (though, if it's anything like Kid Icarus Uprising, they'd just be discarded).
I feel fortunate to live in an area where I have been routinely pickin' up tags for this game, especially from other Japanese players that have already been giving the game their best for the last month and providing some tough competition out the gate. The mode itself is a real blast, and adds another element to the game—and to the Mario formula—that's really exciting. Even if getting my first million doesn't end up being about the destination, I'll definitely be able to say that it was a fun journey.