The weekend isn't even over, but people who do such things for a living are already proclaiming the massively expensive new science fiction epic John Carter a flop. This failure has nothing to do with the quality of the movie itself and almost everything to do with its incredibly incompetent marketing campaign.
Really, though, when was the last time the trailer for a movie made you want to see it? If you're predisposed to see, I dunno, a Sandra Bullock romcom or a hyperactive action movie starring a bunch of real-life Navy Seals, well, the ad campaigns for such movies pretty much let you know they exist. But they won't make you feel like you must see it, like this movie might be the most important thing in the whole world.
People don't go to the movies as often as they once did. The batch of Oscar nominees this year were all box office underperformers. Not surprising, since even the good ones were sold in a safe, respectable manner. Maybe if the ads for War Horse had managed to work in the phrase "A Rebellion of HUMAN GARBAGE" more people would've shown up in theaters.