[pfranz]

Soon after the original iPhone launch Apple posted a letter apologizing for the price drop so soon after the initial launch. "We apologize for disappointing some of you..." http://www.apple.com/hotnews/openiphoneletter/

Like Cook's letter, it was reactionary and came after the price drop was poorly received. They've used this medium quite a few times for specific things (letter against Flash and against DRM). Generally, to clarify their current position or to apologies.

[mapgrep]

Good example, definitely shows this is not "unprecedented" as OP says. Except maybe for the "extremely sorry" part :)