Someone else picked up on this that the hype they try and use is just turning people off.
I know how you feel. It's one of the reasons why I almost never follow any preview information for games. You're less likely to get annoyed if you only keep up to date on recent releases rather than those that are still being developed, being hyped up, hinted at and so forth.
For me, unless the game actually has a price tag on it and can be purchased; I couldn't care less about it. Once it's out, then I'll look at information in the event that there is no demo.
Thus these announcements of impending announcements are just a waste of time, space, bandwidth and whatever else was required in their creation.
In fact there is only one exception right now for me, and that's Team Ico's upcoming game in the Ico universe. But in terms of information, they release very very little over here until a few months before release, so it's not too bad =)