[theDoug]

My first guess would be respect for the company. Secondarily, plenty of results in google reveal that the policy (if somewhat unofficially) is that you can say you work at Apple on your blog, etc, but not really blog /about/ Working At Apple. Even if there's no official policy on it, it's just better taste to say "The thoughts of John Doe" and not represent oneself as "John Doe of Apple."

"There's a PR department for that."

All that said, there are plenty of writers/bloggers who work at Apple. Randsinrepose.com is a personal favorite, and contains the writing work of Michael Lopp who may be an engineering manager at the fruit company. This policy of sorts goes much further back than iPhone/Android or any other blog-hyped non-competition.

[swombat]

Interesting, I never realised that Rands works at Apple...

[jeroen]

Worked, according to WP: http://en.wikipedia.org/wiki/Rands