Addressing questions by @The_Hawk, @cosmichobo and @kyte
Apple’s wording on the matter has been somewhat vague. The official document released to the public requests a serial number, but at least in our case we are currently able to exchange them even if a serial number has not been provided. Apple may change this at some point in the future.
Both Apple Stores and Apple Authorised Service Providers are participating in the exchange program. We (AASP) are exchanging them over the counter, bring the old ones in, we confirm it’s an affected adapter and replace them on the spot. No appointment or reservation necessary. Some Apple Authorised Service Providers may use a different system or method of replacement so contact them beforehand to confirm, and the Apple Retail Store does recommend having a reservation beforehand.
To confirm, Apple is replacing only the AC wall adapter (or “duckhead”) piece, not the entire adapter. The included 1M AC cables are also not affected.