News: Apparently you can buy them used.
Two weeks ago, the MTV Multiplayer blog discovered a disclaimer in the manual for Nintendo's Wii Speak peripheral that the activation code included with it was a one-time use code. This led MTV Multiplayer to speculate that Nintendo was attempting to block the sale of use Wii Speak microphones.
Today, Nintendo UK set the record straight with Eurogamer and confirmed that this is not the case:
"Any consumer who may have misplaced their Wii Download Ticket number for the Wii Speak Channel or require a new number following a Wii exchange may contact their local Nintendo Customer Services department, where they can request a replacement Wii Download Ticket number."
Whether this was Nintendo's plan all along or they were just reacting to the public outcry will probably never be known for sure.