I usually apply the movie industry to the marketing aspect of games.
Two movies as example: the new When a Stranger Calls and...
The original Matrix Trailer.
The Matrix is coming... THAT was it. Brillient!
When a Stranger Calls reveals the ENTIRE plot, and shows you the ENTIRE movie in a condenced format.
The latter example, imho, is the kind of thing that needs to be avoided. Let gamers be fickle, if you play your cards right and have a smart advertising team I think you can get away with it, without sacrificing the early development of the game. Then again I'm a newb, so who knows?
Peace,
Joseph Peabody