According to this CNet article, Harry McCracken of PC World resigned when pressured by SVP Colin Crawford to tone down stories critical of advertisers. I have no idea of the inside scoop on this, and the CNet article is full of anonymous sources, but sadly, I can believe it.
I was never inappropriately pressured from the business side of the magazines, but I have learned that such autonomy is more unusual than not and I strongly suspect the Web has made things worse (everything is harder when journalism has been devalued, both literally and metaphorically).
If the story's accurate, McCracken deserves a big tip o' the hat.