Even though I'm still only considered a "blogger" by many standards out there, I try to follow as closely as I can to the ethics side of things. I've noticed when I call people that I know out for taking free trips from a company here or there, I get a cold shoulder. It really feels like people don't want their meal ticket to go sour sometimes.
Personally, I don't do ads and I pay for trips everywhere I need to go. I'm going broke (seriously) doing this. I don't expect everyone else to, but at the same time, it needs to be balanced.
I don't think this is the solution either. It's been mentioned before, but why does the advertising in gaming sites need to be 100% gaming related?
You have access to the most widely sought after demographic in advertising, why waste it on advertising for games they probably already know about. If I'm reading a review about Diablo III a banner for the game on top of it isn't much use. I'm at the point where I'm actively looking for more information on the title, that banner is a wasted opportunity.
Gaming sites could still be profitable and negate the effects of PR on their editorial content if they just went with different kinds of advertisements. Tell me about movies or TV shows I might not know about. Even a Doritos & Mountain Dew ad is miles better than the game you're reviewing.
I think no gaming site or mag should advertise games. I know most tell themselves that the editorial and commercial departments are completely separate and don't interact with each other, but that quickly falls apart when the publisher in question represents a significant portion of the advertisement pie.
tl;dr: It should be completely unethical to advertise the stuff you're criticizing and that ALL gaming sites are unable to see this is troubling to say the least.