iLounge was apparently first mention the presence of a possible authentication scheme, and Boing Boing Gadgets was the first to find some kind of chip inside the headphones—whether or not it was an authentication chip was unknown.
V-Moda, one of the manufacturers who announced shuffle-compatible headphones last week, just confirmed to us that yes, an authentication chip IS "required to enable to volume control functionality with the new shuffle (as well as the latest gen of iPod and MacBooks)." The difference here is that iPods and MacBooks worked with headphones that didn't have the authentication chip. The shuffle does not.
V-Moda also says that they've collaborated with Apple for the past few months developing the technology. It seems safe to conclude two things. One, manufacturers who want their headphones to work with the shuffle need to work with Apple in order to get access to the tech inside the authentication chip. Two, only people who Apple "like" are going to get this tech and make compatible headphones—but it's likely that Apple likes almost anybody with the money to pay for licensing.
Whatever the consequences, it does look like Apple is going down the path of locking down headphones, hoping to crunch out another revenue stream from all the manufacturers offering ways of getting sound from your iPod to your ears, whether it be through earbuds or through car adapters.
Image courtesy Boing Boing Gadgets