Nintendo's online store is no longer offering the Nintendo Wi-Fi USB Connector. According to the item's listing, it has been "discontinued until further notice." Tipster BPM speculates that Nintendo's deal with Buffalo Technology
has ended. We find it more likely that the proliferation of cheap wireless routers, which work even with non-Nintendo devices
like computers, caused demand for the item to shrink.
Nintendo suggests the Wii LAN Adapter
as a potential substitute for the USB dongle, or you can just go buy a wireless router.
Of course, no activity on Nintendo's part is any fun without some idle speculation. With that in mind, the real
reason they've discontinued this item is because they're going to release a new version that has a picture of Mario on it.