Super Mario 3D Land will use Streetpass for the exchange of items and other things and assist blocks will provide special items inside levels. The information was derived from the back of dummy packages from the Japanese versions of the game.
My problem isn't being able to ignore it, but it being a power-up in the first place. If it was some post-content special thing (like the flying power-up in Super Mario Galaxy), that'd be different, but I doubt that's the case.
My only experiences with it so far were racing people's ghosts in Ridge Racer, fighting their AI in DOA, and getting their character/dog in Nintendogs, but those were all very cool. It would be good to be able to exchange that stuff online with Friends, but it's also neat when you get a surprise from a stranger.
@Jargon Yeah, I hope the 3DS blows up, if only to get much, much more out of the social features. Which were probably meant more for Japan, anyway. I think they'll really help the momentum over there continue to build. Especially with Tomodatchi Collection and Girls Mode, and such.
By the way, weirdest use of Street Pass: Viral leaderboards in Ridge Racer. What the hell?
The reused assets bug me. It's nit-picky I guess, but the big coins and mid level markers are straight out of NSMBWii. If they were designed even slightly differently I wouldn't be bothered by it so much. I'm weird I guess.