The 3DS's StreetPass feature maximises the console's portability by offering interactive features with no user input required, but Nintendo hasn't ignored the machine's at home functions, creating a system called SpotPass to enable the 3DS to communicate via the Internet whilst in Sleep Mode.
Working in a similar fashion to Wii's WiiConnect24 service, SpotPass allows the 3DS to seek out new information simply by being in Sleep Mode near a WiFi hotspot. In fact, Sleep Mode activates SpotPass and StreetPass simultaneously, so even whilst the machine is searching for online data it can be interacting with local consoles too.
Nintendo gave various examples of the kind of data that will be downloaded, including rankings, ghost data, notifications and new free software. Considering the DSi has just two free downloadable applications at present don't get too excited about the promise of new free games every week, but it's a start. The company states that it will only be the availability of free software that's sent to your 3DS, not the software itself, although the machine will be connected to the Internet and therefore able to download the free game or trial straight away.
Nintendo will allow you to set how much information you want to give or receive, with a set of privacy controls letting you determine your 3DS's level of engagement with the Internet.
Wherever you are, it seems the 3DS will be able to send and receive new data all the time. Skynet is only a few small steps away.