Nintendo has informed us that National StreetPass Weekend is happening on December 14 and 15 and yes, this is a serious holiday. While I'm content sticking to StreetPassing each year during PAX and calling it a day, this should be a nice little treat for more dedicated players.
The North American Nintendo Zones (find yours here) will be mixed about, meaning you'll have the opportunity to interact with folks from other areas. Those dancing Miis at 0:30 suggest that good times will be had by all who participate. Nintendo in the YouTube age sure is a sight to behold.