Animal Crossing: City Folk is already out in North America, and alongside it the new Wii Speak USB microphone which supports voice chat over the Wii Speak Channel.  Nintendo confirmed earlier this month that the only way to access the new Channel is through a special 16-digit "Wii Download Ticket" activation code, available only with the purchase of the Wii Speak microphone.  The Wii Speak Channel currently cannnot be installed through any other normal update, so you'll need to purchase the microphone if you want in; you probably wouldn't have any reason to check out the Channel without it anyways.

The obvious question is, what happens if a user loses their Wii Download Ticket number for whatever reason?  Nintendo today reassures that it will be able to provide replacement activation codes, but users will need to contact their nearest and dearest Nintendo Customer Service department and request one.  Which probably means they'll need to explain why they'll be needing another activation code, a likely scenario when the peripheral never came with one in the first place for example.  Still, it's not a change for the worse considering Nintendo wasn't originally planning on providing any replacement codes regardless of whether or not they were lost or stolen.