Is that necessarily a bad thing though? To be fair, Apple, Facebook, and Google have had by far the largest impact on consumer technology in the last decade. Obviously, they're newsworthy and interesting.
To me, a good measure for whether an article should be on HN or not is whether people can learn something useful from either the article or the discussion surrounding the article. I think we can all learn from their strategies and actions, and the conversations surrounding articles about Facebook or Google are usually filled with insightful comments (maybe not so much with Apple articles).
Apple, Facebook, and Google are discussed everywhere, all the time, on all tech news venues ad nauseum. That is why I personally don't care for their appearances on HN. You are right though, often the commentary is outstanding compared to what you would find elsewhere.
Worthwhile and insightful stories are good. Stories that trigger worthwhile and insightful dialogue are good.
What's not so good is yet another link of Gruber dutifully cheerleading whatever Apple does, followed by comments about how all Gruber does these days is dutifully cheerlead whatever Apple does.
To me, a good measure for whether an article should be on HN or not is whether people can learn something useful from either the article or the discussion surrounding the article. I think we can all learn from their strategies and actions, and the conversations surrounding articles about Facebook or Google are usually filled with insightful comments (maybe not so much with Apple articles).