Apparently, Google's Nexus One has the hardware capability to connect to wireless-N Wifi networks. iFixit, in their dismantling of the smartphone, found that the wireless NIC was a Broadcom BCM4329EKUBG, a model that does support the N wireless standard.
Google customers have been confused as to the actual software capabilities for such connections, and it's become clear that the "N" was taken out of the spec sheet when it was determined that Android wasn't reliable enough with the connection to warrant spec sheet love. Nevertheless, users continue to report connectivity on their N networks, and modders like cyonogen have released modded Andorid ROMs with N connectivity enabled.
Android and Me reports that Broadcom and Google have released a new wireless driver for the Nexus One that specifically addresses wireless-N connectivity, and seems to have fixed the problem. Users with the wherewithal to install custom drivers in their OS are able to take advantage of this functionality. There is speculation that Google will be packaging this driver update in Android 2.2, codenamed Froyo. As the driver is fully functional, and for lack of an official announcement, this seems to be the most likely scenario.