I've decided to post a reply before reading any of the comments, in order to offer an unspoiled opinion on the issue. While I am still a gamer (even though I play a lot less nowadays than I'd like to...), I've also been working in the industry throughout all my professional career of 15 years now, and perhaps I can offer some insights. I'll try to be as open as I can; but I'm still bound by a lot of NDAs and such, being a relatively high-level guy at our studio with access to a lot of classified information.
Video game development has become incredibly complicated, time consuming and expensive. Even titles that you'd consider a safe bet are in fact a risky investment of millions of dollars, and their success or failure will depend on many different factors. It is really the only reasonable option for the publisher to try to keep control of as many of these factors as possible.
One of the most important element here has to be the marketing campaign of the game, and a lot of it is focused on what information should be revealed and at what time. There are many ways for this, including trailers released on the internet, using licensed music and/or expensive CGI, custom press events with playable versions, large expos like E3, and even one-time special events and closed-door stuff.
One of the best examples is Blizzcon, which obviously isn't just about game announcements - but still they're always a part of the program. Blizzard has to spend an incredible amount of money on the organization, infrastructure and other elements, and in terms of the new games, all of this is justified because the event has no competitors in the media, so they can have a lot more attention to their announcements. This is also the reason behind Quakecon and a few other similar annual events. But there are sometimes other, one-time events for games, and they may include more elements that also cost a lot of money.
Premature leaks about the game will inevitably disrupt the carefully planned and organized and expensive marketing plan. They may also reveal any kinds of gameplay, graphical, online and other features that are not yet finalized and may have to be cut before even publicly announcing them, which will generally lead to negative response from the customer base; and usually from all the other internet users (NEOGAF, 4chan etc).
Any reasonable gamer should see how such leaks can be incredibly damaging. Just for a start, the resulting scrapping of existing marketing plans will cost a lot of money (canceling reservations and trailers for example), so the publisher will either have to cut the number of events and trailers and such - or end up spending more.
The other major loss could appear in sales: cutting features in later stages of development could drive away potential customers, and a premature announcement could even affect sales of other titles. This could eventually lead to cancellations of other titles or lay-offs at various studios or budget cuts on other titles.
A game journalist should be even more aware of the possible negative effects of releasing information about such leaks, or behind the scene stories about troubled development.
Make no mistake, I am quite aware of the complex moral and ethical issues related to this profession, as I've been a freelance writer for a local game magazine in sometime 1997-2004 or so. But because of this I believe I'm also aware of the responsibilities of the job, too. I also understand that there are a lot of competing media outlets, and because of this, there may be a push to use any possible means to gain more views and recognition by either being first or simply following other outlets.
Still, I do believe that the press - in general - does have an obligation to inform the public about all kinds of things. But I also believe that any kind of product should first and foremost should be judged by its own merits. Thus the journalist's first responsibility in such cases is to very carefully consider every possible consequence that could result from publishing the undisclosed information that has been delivered.
I know this is an extreme comparison, but consider this example: CNN learns that US special forces are planning a risky operation behind enemy lines to rescue a hostage. Revealing this story would compromise the mission and probably lead to loss of life. In my opinion, any responsible editor or journalist would decide to hold back the information.
Video games are obviously without such high stakes, but I believe that the same moral standards should still apply. If the story can have damaging consequences, then it is not right to publish it.
On the other hand, I firmly stand by the policy of publishing any kinds of behind the scenes information after the game's release. At this time, demos have been released, the title has been reviewed, complete walkthroughs and such have been posted on Youtube, so the game is now standing on its own. Any additional information will probably not have significant negative effects on either the sales or the careers of the developers and marketing people and others involved in its creation.
Lastly, I also see that any moral or ethic standards are always subject to debate. Others may have different considerations and thus they can make different decisions. However, they should also accept the consequences of their choices. I think that it is a publisher's right to respond to a media outlet's damaging moves by denying them special treatments like invitations to press events or free review copies.
And now I'm going to read the thread to see what others think