@ Kasz: it doesn't always have to be that way.
Our site has its own department that settles the advertising with the strict rule that no matter who advertises, the editor-crew is entirely free to judge a game the way it wants, whether that be good or bad. In the end, if gamers keep flocking to the reviews, publishers have no other option than to advertize, seeing how it's the easiest way to reach their audience... Gamers.
Sites that differ from this strategy, are sites that are probably too afraid to lose exclusive deals / money. If that's the case, good riddance with those sites imho