Honestly? I'd like to use a word that isn't so loaded... but here is one of the basic things.
In games journalism, practices that just don't fly in journalism proper do. It is a small community, really limited to about five cities from what I understand. Everyone knows everyone else. For a journalist, this can be a good and a bad thing. There is a level of professional networking that is required, and a level of civility that is required, but... it's simply not ethical to be friends with your sources.
Because a friendship is a fundamentally different kind of relationship. Friends will try to ensure each other's best interests over say, some random stranger they've never met... and that raises a fundamental conflict of interest. Journalists have to skirt that line, and they have to be able to recognize when that line has passed. When you become friends with someone, you've got to get off the beat. It's just too grey at that point, you need to let another journalist step in.
Now... this isn't to say that you can't say anything about your friends or their experiences or games. Some of the most powerful journalist is from these sort of personal and moving stories, but the reader understands the context in these personal tales. They are stories that journalists are telling us about them and their friends.
I keep hearing people throwing this word "objective" around and... the fact of the mater is there just isn't objectivity. Humans can't do objectivity, but journalists can strive for it. That means minimizing the influences that they have and disclosing what they determine might still bias them in a non-trivial way.
You have brought up a very legitimate kind of collusion as well. Advertisers have been long suspected of basically being able to 'buy' reviews from Incredibly Generous Newsmakers by paying for ads on their sites and using that leverage to influence and pressure journalists through the companies they work for. This is troubling as well, and I believe it is systemic.
It manifests even more so, as shreckfan mentioned, when we look at youtubers and the resent terms for Shadows of Mordor. I can't trust these sort of reviews anymore... I have to look for the disclosures every time. That kind of sickens me. It's legal, but I question the ethics.
Another point I like to discuss is the use of the numerical rating system in modern game reviews, which I feel decontextualizes critique. I mentioned before that there really isn't such thing as objectivity, and that's doubly so in editorial work. While you have an objective mindset when reviewing, the experience is still going to be very personal. As such, you need to contextualize it. You need to tell us how you enjoyed the mechanics, how you felt about the characters, if there were bugs that detracted from your experience, how it felt to play. All of these things paint an immage of what it is like to play the game for us.
But then reducing that image to 7.5 out of 10... what does it mean? Where the mechanics week but the story solid? Did the story suffer but the mechanics tow the line? Did a particular character not feel fleshed out? These are important aspects of the situation which we get no hint of from a simple abstraction...
And then that abstraction is taken, put into metacritic, mixed in with more abstraction with a secret formula and then out pops an entirely abstract and devoid of context number... which can then determine raises.
I think that that contributes to the corruption largely too, and it just seems wrong to me. I don't feel like anyone is being judged on their merit in that situation rather than just being judged, arbitrarily... with no context.
