Yeah, but in the entire history of people quitting and writing "letters to the editor", has any manager ever actually read it and thought anything other than "whatever, dude wasn't on board, glad he left"?
Do you really think Sergey Brin or Larry Page or Eric Schmidt are going to read this and think "oh man, we better change what we're doing".
Nope.
People who are fans of MS are going to read it and say "yeah, see, I told you google is evil. Even his 15 year old daughter had a poignant critique of Google+ that shows she's not only wise beyond her years, but that Google+ sucks just like I always thought already."
It just doesn't sound genuine.